Description of a New Species of Cosmarium (Corda), of Staurastrum (Meyen), of Two New Species of Closterium (Nitzch), and of SpirotÆnia (Bréb.)

Frond very minute, constriction very obtuse and shallow; segments in front view broadly elliptic, outer margin bordered by a few very minute, opaque tubercles or granules; end view broadly clliptic.

A small pool, near the ice-houses, on the Pipers-town road, county of Dublin.

Frond very minute; in front view about one fourth longer than broad; constriction wide, shallow, forming an obtuse angle ; isthmus wide; segments broadly elliptic, outer margin bordered by a few (5—7, often 6) very minute opaque superficial tubercles oi’ granules; side view narrower, about twice as long as broad; constriction a mere gentle depression or concavity at each side, segments forming about two thirds of a circle, outer margin, as before, bordered by a few minute, opaque tubercles; end view broadly elliptic. Sporangium unknown.

Length of frond, to breadth, to depth, of an inch.

Plate XII, fig. 11, front view; fig. 12, side view; fig. 13, end view; figs. 14 and 15, dividing fronds. All magnified 400 diameters.

The very minute size, combined with the obtuse, shallow, but decided constriction, and, above all, the outer margin of each segment being bordered by the minute, opaque, or dark granules, render this little species very distinct, causing it to be almost unnecessary to compare it with any other.^*It is intermediate in size between C. bioculatum and C. tinctum; but, besides the tubercles, it is quite distinct from them by its broader isthmus and more broadly elliptic segments.

Frond minute; segments smooth, broadly lanceolate, extremities acute, minutely apiculate; end view triangular, angles minutely apiculate, sides concave.

Sphagnum ponds, Featherbed bog, county of Dublin, coating the moss.

Frond minute, about as broad as long, constriction forming a deep, acute notch at each side ; supposing the constriction absent, the frond would present an orbicular outline; segments smooth, in front view broadly lanceolate, the outer margin slightly more convex than the inner, their opposite lateral extremities acute, minutely apiculate (though the apiculus is sometimes difficult of detection); end view triangular, angles somewhat inflated, minutely apiculate, sides concave at the centre. Sporangium orbicular, spinous; spines numerous, somewhat inflated at the base, their extremities subulate, acute.

Length of frond, ; breadth, diameter of sporangium, including spines, ; not including spines, of an inch.

Plate XII, fig. 16, front view; fig. 17, angular view; fig. 18, end view; fig. 19, dividing frond; figs. 20, 21, 22, conjugating fronds; fig. 22, showing mature sporangium. All magnified 400 diameters.

This species agrees somewhat with Staurastrum orbiculare, Ralfs, in its general external outline; but it differs therefrom in its segments being lanceolate, not semiorbicular (the constriction being not linear, but a gaping notch), and in the opposite lateral extremities not being rounded, but acute and apiculate. Its lanceolate apiculate segments separate it from S. muticum, Breb. The same characters separate it from S. Pygmœum, Breb., which latter has cuneiform segments, as well as the extremities of the spines of the sporangium being bifurcate, not subulate and acute, as in this species. From S. dejectum, Breb., it may be known by its lanceolate, not elliptic, segments, and its merely apiculate, not spinous, extremities. Its lanceolate, pointed, not elliptic or reniform, segments separate this species from S. brevispina, Bréb., while the mucrones of the latter are rather larger, though not more conspicuous.

Frond rather slender, scarcely curved, nearly straight, linear, ends truncate; fillets indistinct; empty frond, very finely and closely striate.

Several pools, Dublin mountains.

Frond rather slender, about fifteen to twenty times longer than broad, scarcely tapering, lower margin very nearly straight, upper also very nearly straight, but slightly depressed towards the truncate ends, giving the frond a nearly straight outline. Endochrome with indistinct fillets and a conspicuous series of large granules. Empty frond generally colourless, sometimes faintly reddish near the ends, very finely striate, the latter character sometimes difficult of detection in mounted, but quite evident in fresh, specimens. Sporangium unknown.

Occasionally a distorted specimen is met with, slightly geni-culately bent, or a segment sometimes presents a somewhat irregularly curved form; but a similar circumstance is not unfrequently to be noticed in Docidium Ehrenberghii, which is a straight form. ‘

Length of frond, to breadth, of an inch.

Plate XII, fig. 23, frond with endochrome; fig. 24, empty frond. Magnified 200 diameters.

This species is decidedly the straightest and most linear in form of all the genus Clo-stcrium, and it -will therefore be necessary to contrast it with those only whose curvature and tapering are the most slight.

It may be advisable to contrast this species with C. didy-motocum, Corda, C. obtusum, Bréb., C. amblyonema, Ehr., C. intermedium, Ralfs, C. angustatum, Kütz., and perhaps C. juncidum, Ralfs, and C. gracile, Breb. This species agrees with C. didymotocum in its nearly straight frond and truncate ends, but they differ in the following particulars :— In the former the frond is far more slender than in the latter, which is stout, and in the former the upper and lower margins are parallel or nearly so—in the latter the lower margin is frequently curved upwards at the end, and the upper margin is convex; and in the former the empty frond is far more finely striate than in the latter, while it is more nearly colourless. C. directum is a more slender, more linear, more bacillar form than C. didymotocum, and, so far as comparative outward form merely and length and breadth are concerned, may be said to bear a relationship to that species somewhat similar to that which Colsterium juncidum does to C. angustatum, or which Docidium Ehrenberghii does to D. nodulosum. Indeed, I do not think there would be a possibility of confounding these two Closteria if seen side by side. C. directum agrees with C. obtusum, Breb., in its scarcely tapering frond, but it differs from that species in its truncate, not rounded, ends, as well as in its striate, not smooth, empty frond. The latter, indeed, appears to me more to resemble a somewhat slightly curved Penium (so to speak) than a Closterium, as, indeed, M. de Brebisson himself remarks, nor does he refer to moving granules at the extremities. C. directum agrees also with C. amblyonema, Ehr., in its scarcely tapering frond; but the former differs from the latter in its smaller size, in its straighter outline, in its truncate, not broadly rounded, ends, and in its striate, not smooth, empty frond. C. directum agrees with C. intermedium and C. angustatum in its scarcely tapering frond, but differs in the ends being truncate, not rounded, and the strife far more fine and close; moreover, those species are considerably more arcuate. C. directum differs from C. juncidum, Ralfs, and C. gracile, Breb., by its straight frond, not curved downwards at the ends, and by its much less slender fronds.

Frond gradually tapering, curvature slight; lower margin very slightly concave, inclined upwards at the tapering, conical, truncate ends; endochrome with several fillets, and a single longitudinal series of large granules ; empty frond very finely striate, reddish near the ends.

A pool at the top of Howth, conjugated; several pools, Dublin mountains.

Frond from about ten to fourteen times longer than broad, somewhat stout, slightly curved, tapering very gradually from the centre, towards the ends more rapidly; lower margin slightly concave, and inclined upwards near the conically attenuated, truncate, reddish ends; upper margin gradually convex, sometimes very slightly depressed near the ends, owing to the upward inclination of the apices; endochrome bright green, reaching near the ends, and having beyond it, close to the apices, the active granules —large granules in a single series,longitudinal fillets several; empty frond frequently slightly reddish, especially near the ends—longitudinal striae very fine and very numerous, in mounted specimens very difficult of detection, but in recent very readily made out. Sporangium large, orbicular, or very broadly elliptic, smooth, placed between the empty fronds, which are for some time persistent. Conjugation taking place soon after self-division, one, the younger segment of each conjugating frond, is much shorter than the other, the older, longer segment, each of which lies in a parallel position, pointing in the same direction.

It is with much gratification that 1 take the opportunity to name this species after a well-known microscopist, Andrew Pritchard, Esq., author of several valuable additions to microscopical literature. When, at my request, Mr. Pritchard did me the honour to permit me to dedicate this species to him, he quaintly added that his only objection was that he thought his name too long. I do not assent to this; but, even if it were, I might reply, that his services in the cause of microscopy have indeed been long, and far more than deserving of this inadequate compliment.

Length of frond, to ⁠; breadth, to ; diameter of sporangium, inch.

Plate XII, fig. 25, frond with endochrome; fig. 26, empty frond; fig. 27, conjugating fronds with sporangium. All magnified 200 diameters.

To me it seems that there are only four species with which there is any likelihood of this Closterium being confounded, and those are—Closterium turgidum, Ehr., C. attenuatum, Ehr. (opposed as may seem the specific names of those species), C. acerosum, Ehr., and C. lanceolatum, Kg. Closterium Pritchardianum agrees with C. turgidum in its gently curved but slightly tapering frond, in ite lower margin being curved upwards towards the reddish apices, in its endochrome possessing longitudinal fillets and a single series of large granules, and in its empty frond being finely striate; but the former differs from the latter in its less stout and less curved frond, in its conical and truncate, not broadly rounded, ends, and in the striae seen on the empty frond being far more fine and close. C. Pritchardianum agrees with C. attenuatum in the size and general curvature of the frond; but the former differs from the latter in its conically tapered, truncate ends, not suddenly contracted (more or less like the handle to an oar) into a conical point, and in the striae on the empty frond being far finer. The lower margin being curved upwards near the extremities, seems to give this new species some resemblance to C. acerosum, Ehr., and to C. lanceolatum, Kg.; but I believe the somewhat reddish, truncate apices and longitudinal striae will readily distinguish it from both. It is less slender in proportion to its length than C. acerosum, more so than C. lanceolatum, and the upturned conico-truncate ends seem to me very characteristic. There appears to me no danger of mistaking this form for C. Ralfsii, so decidedly distinguished by its turgid, ventricose body, and prolonged, beak-like extremities.^*

Closterium is a genus in which it is difficult always accurately to define in words the specific distinctions, resting in allied species, as they frequently do, on more or less stoutness or slenderness of frond, more or less degree of curvature, more or less rapidity or slowness of tapering, more or less acute or more or less broadly rounded or truncate apices, and, in the striate species, on more or less fineness or coarseness of, or distance between, the striae. But I believe such distinctions to be here equal in value, and quite as reliable, as more striking characters in other genera, different allied species of Closterium possessing such in different and constant degrees of combination; and I cannot admit, because the distinctions between certain neighbouring species, as compared with each other, may sometimes depend on a more or less as regards certain common characters, that therefore good and quite distinguishable species do not exist in this genus. Difficult as it may be (to me at least) to define those distinctions, there is at least always a tout ensemble, a general contour, a certain definite combination of characteristics in the same species, whenever met with, which, when they impress themselves on the eye and memory, render the identification by no means difficult. I have never seen even a solitary instance of conjugation except of like admitted species with like. 1 therefore imagine, on the whole, it may be quite possible that certain of the Closteria described by Continental writers, which (if erring, at least, I apprehend, erring on the right side) I have been disposed to think are identical with previously described forms, may be really quite distinct, could one but see the actual specimens. But be this as it may, however I may fail to convey by my description the valid distinctions which I conceive to exist between the foregoing Closteria and the nearest allies of each, I have no doubt of them myself, from a careful examination of the living specimens; and I am glad to say that, having had the honour to submit specimens to M. de Brébisson, my own opinion is coincided in by that high authority.

Frond cylindrical, but tapering near the truncate ends; endochrome a single, rather closely wound, spiral band, leaving a minute clear space at each end, often containing one or more free granules.

Featherbed Mountain, co. Dublin, in small pools; rare.

Frond minute, five to eight times longer than broad; cylindrical, but tapering towards the extremities, ends truncate; endochrome at first a single, rather closely wound, spiral band, its revolutions few, frequently afterwards scattered and indistinct in each fully grown frond, leaving at each end a minute, semicircular, clear space, in which there occur one,, or perhaps two, free granules; gelatinous investment very evident.

Length of frond, breadth, of an inch.

Plate XII, figs. 28, 29, mature frond ; figs. 30, 31, recently divided fronds. All magnified 400 diameters.

The cylindrical frond tapering towards the ends in this species renders it somewhat like in outline to that of Spirotcenia obscura, Ralfs, with which it also agrees in having a clear space containing often one, occasionally two, or even three, free granules; but it differs from that species in its greatly more minute size, in its truncate, not broadly rounded, ends, and in its endochrome forming a solitary, not several spiral bands. With S. condensata, Breb., 8. muscicola, De Bary, and S. erythrocephala, Itzigsohn, it agrees in its single-spired endochrome; but its tapering, truncate ends well distinguish it from the broadly rounded ends of the two former and from the acute ends of the latter, besides other characters in each instance, as is readily seen by the foregoing description. From Endospira closteridia, Breb., —a species which I apprehend ought to be referred to the genus Spirottenia—this form is distinguished by its larger size, by its straight and cylindrical, not arcuate or sublunate, outline, as well as by its truncate ends and terminal clear space. Its larger size, truncate ends, and broad spiral band, readily separate this from the following new species.

Frond very minute, slender, fusiform, ends subacute; endochrome obliquely parietal, scarcely spiral.

Featherbed bog, Dublin mountains, in Sphagnum pools, on the moss. Not unfrequent, but readily overlooked on account of its very minute size.

Frond very minute, five to eight times longer than broad, fusiform, ends subacute; endochrome a single, oblique, parietal band, often scarcely forming a spire, but frequently presenting to view apparently three darker portions of elongate form, one towards each end at the same side of the frond, the other at the middle at the opposite side, thus leaving between them a very narrow, eccentric curved, clear space; gelatinous investment of great tenuity, and rendered evident only by preventing the contact of foreign bodies and by holding together the recently divided fronds.

Length of frond, to ⁠; breadth, to of an inch.

Plate XII, figs. 32 to 43, mature and recently divided fronds. All magnified 400 diameters.

The scarcely spiral, sometimes scattered, endochrome, at first made me hesitate to consider this plant as belonging to Spirotienia; but as it frequently seems to form an oblique parietal band, and the self-division, as in other species of the genus, is oblique, and the divided fronds held together by a gelatinous investment, there can, I apprehend, be no doubt but that in this genus this minute little form finds it proper location. Moreover, I have seen some specimens in which the endochrome clearly made a spiral turn, though in the majority of instances the condition I have tried to describe above is seen; and not unfrequently, as in other species, a confused or irregular condition of the endo-ehrome exists. Its very minute size, subacute extremities, and without a clear space, easily distinguish this from other described species of Spirotmnia. It really appears to approach more to Endospira ctosteridia, Breb., Kg. (which plant, as I before stated, I apprehend should fall under this genus); but it is distinguished by its fusiform, not at all arcuate, and by its narrow, outline, as well as by its obscurely convoluted, not distinctly and smoothly spiral, endochrome.