The form with concave sides approaches to C. anceps, Lundell, but it is larger, and the ends are not emarginate. I observe that Wolle's figure of C. anceps (“Desm. of U.S.,” pl. xviii., fig. 11) differs considerably from Lundell's. The convex form resembles C. parvulum, Brébisson, but is also much larger. The three outlines which I give were taken from a gathering in which the plant occurred rather plentifully. Mr. W. B. Turner informs me that he has seen from India a plant something like mine, and thought of giving to it the name of C. varians. Herr G. Lagerheim tells me that he has had my plant growing in a greenhouse at Berlin for two years: he does not mention the locality whence he procured it, but this could hardly have been New Zealand.

Cosmarium curtum, var. attenuatum, Brébisson. Plate II., fig. 16.

Sufficiently near to the European species, I believe, to permit identification. It will be noticed that this New Zealand form has a slightly elliptical end-view, being narrowed as seen from the side. It is just possible that this may be sufficient to distinguish it from Brébisson's plant, or, at least, to suggest that it should be named “forma compressa.” But for the present I prefer leaving it as it is, subject to future revision. In dimensions it is rather smaller than the type.

Long., 35 μ; lat., 15 μ; crass., 10 μ.

Otaki.

Cosmarium retusum, Perty; var. læve, Roy and Bisset Plate II., fig.17.

This plant differs from Perty's type in the total absence of granules. Lundell (“Desm. Suec.,” p. 36) remarks that the granules of C. retusum are not easily observed; but they are undoubtedly absent in the New Zealand as in the Japanese form.

Long., 17.8 μ; lat., 13.5 μ; crass., 7 μ;.

Hawke's Bay; Otaki.

The dimensions given are rather smaller than those of Roy and Bisset (“Japan Desm.,” p. 195), but the plant seems to be otherwise identical.

Cosmarium pachydermum, Lundell, forma intermedia Plate II., fig. 18.

Long., 81 lat., 55 μ; crass., 19 μ;.

Christchurch; Hawke's Bay; Kaitoke; Otaki.

This plant seems to be intermediate in size between Lundell's original type and Nordstedt's “var. minus” (“Norges Desm.,” p. 18). The segments are quite round, as in the type; but in side-view they are rather narrower and more attenuated.

The plant which I reported as “Cos. ralfsii, var. β” (“Trans.,” 1882, vol. xv., p. 239), may perhaps have been a still smaller form of the same plant; but I have not now any specimens to which to refer.

* Cosmarium trilobulatum, Reinsch, var. basichondrum, Nordstedt. Plate II., fig. 19.

Long., 18 μ; lat., 12 μ.

Otaki.

My measurements are a little less than those given by Professor Nordstedt (“Alg. of N.Z.,” p. 57).

Cosmarium cordanum, Brébisson, forma minor. Plate II., fig. 20.

Long., 30 μ; lat., 15 μ; crass., 12 μ.

Rutherford's Swamp, Otaki.

I have never seen the original figures of this plant, and have judged from those given of it by Wolle (“Fresh. Alg. of U.S.,” pl. lx.) and by Turner (“Journ. Roy. Micr. Soc.,” Dec., 1885). With these it agrees nearly in all but size, and perhaps a little more angular form in side-view.

* Cosmarium repandum, Nordstedt. Plate II., fig. 21.

I think my specimens have rather more sinuous sides than the type.

Cosmarium speciosum, Lundell, forma genuina. Plate II., fig. 22.

Long., 50 μ; lat., 26.8 μ; crass., 17 μ.

Hawke's Bay.

The dimensions of this plant seem to vary. Wolle says that the American forms are much larger than the Swedish.

Cosmarium speciosum, Lundell, var. simplex, Nordstedt. Plate II., fig. 23.

Long., 40–45 μ; lat., 28–32 μ; crass., 15–17 μ;.

Hawke's Bay.

This plant is less angular than the type; but I scarcely like to consider it at present as a new variety. Hereafter it may be separated on account of its rounder form. ^*

* Cosmarium sub-speciosum, var. validius, Nordstedt. Plate II., fig. 24.

This plant, in vol. xv. of our “Transactions,” I reported as C. speciosum, var. inflatum. Professor Nordstedt has placed it more correctly as above.

Cosmarium regnesi, Reinsch, var. ornatum, var. nov. Plate II., fig.25.

Frond very minute; constriction shallow, wide, and curvilinear; segments in front-view irregular, sides very short, cut into three minute lobules with concave edges; angles between the lobules sharp; ends concave. Cytioderm bearing at each side of each segment three granules arranged triangularly. Segments in side-view sub-fusiform, tapering gradually to rounded ends; two minute granules visible on the face and two others on each edge: of the last, one pair are near the base, the other near the end. End-view angular-elliptical, a minute granule marking each quasi-angle.

Long., 9 μ; lat., 9 μ; crass., 2.5 μ.

Christchurch.

If I may judge by a tracing sent to me by Mr. W. B. Turner of Reinsch's original figure of this plant, and by a figure of Mr. Turner's in the, “Naturalist,” February, 1886, the plant herein described is more ornate than the original. Some specimens, however, in slides sent me from England a few years ago by Mr. Joshua, are nearer to this New Zealand form, though not exactly similar. Reinsch's figure is, as I understand, by no means a good one. The plant is exceedingly minute, and is scarcely to be made out with a less power than 1,000 diameters. It appears to have sometimes a pink tinge.

Cosmarium holmiense, Lundell, forma minor. Plate III., fig. 26.

Long., 54 μ; lat., 35 μ; crass., 23.7 μ.

Hawke's Bay.

Shorter, and not quite as wide as the original type. The American form (Wolle, “Desm. of U.S.,” p. 68) is even narrower. The dimensions here given are constant in many specimens.

Cosmarium, naegelianum, Brébisson, var. latum, var. nov. Plate III., fig. 27.

Frond small; constriction deep, linear, narrowed at the mouth; segments in front-view nearly twice as wide as long, with slightly convergent sides; edges crenulate, with five crenations at each side; ends wide, plane, or very obscurely crenulated. In side-view, segments sub-rectangular, angles rounded; in end-view elliptical, with a very slight median inflation and an obscurely crenulate edge. Cytioderm minutely punctate, the puncta obscurely arranged in transverse rows when in side-view. Zygospore globose, spinous with short sharp subulate spines.

Long., 25 μ; lat., 23.8 μ;, crass., 11 μ; diam. zygosp. incl. spin., 32.7 μ; long. spin., 3 μ.

Christchurch; Hawke's Bay; Otaki.

A plant of the series of C. crenatum, Ralfs; but proportionately shorter and broader, and the crenulations of the ends in front-view are so obscure that the end often, appears nearly straight. C. naegelianum, as figured by Wolle (“Desm. of U.S.”), is narrower than this New Zealand form, but his description otherwise corresponds. This plant differs from C, sub-punctulatum, Nordstedt (“Alg. of N.Z.,” p. 47), in the absence of the granules which are conspicuous in that form. The zygospore is new.

Cosmarium turnerianum, sp. nov. Plate III., fig. 28.

Frond moderate; segments in front-view twice as broad as long, or more; constriction deep, linear, and somewhat wide, so that the segments do not closely approximate; segments sometimes circular, sometimes trapezoidal, the edges deeply sinuous with ten wide crenulations; cytioderm marked by a number of granular inflations corresponding to the crenulations of the edge, giving an appearance to the frond of grooves radiating from the centre; in the median space a series of seven smaller inflations in a row on the base of each segment. A frond with circular segments is almost regularly elliptical, the ends at the constriction somewhat sharp. In side-view, segments sub-elliptical, narrow, ends rounded, edges very obscurely crenulated towards the ends, and with a slight inflation towards the base marked with minute inflations. In end-view, frond sub-elliptical with sharp ends, the thickness variable; a slight median inflation visible, and the granules arranged in transverse series.

Long., 36–40 μ; lat., 40 μ; crass., 14–20 μ.

Hawke's Bay.

This plant approaches C. cyclicum, Lundell, especially when elliptical with rounded segments, but it is smaller, has a wider sinus at the constriction, with more conspicuous “grooves” on the frond, and the row of granules at the base of each segment, producing the inflation in side-view, is quite distinctive. Lundell gives two variant figures of C. cyclicum, neither of which has trapezoidal segments. C. cyclicum, var. arcticum, Nordstedt, is more angular than Lundell's type, but its edges are irregularly incised, and it has not the rows of granules which produce the inflations of our species.

I have ventured to attach to this plant the name of Mr. W. B. Turner, who has been kind enough to give me much help.

Cosmarium sub-cyclicum, sp. nov. Plate III., fig. 29.

In 1882 (“Trans.” vol. xv., p. 241) I reported this plant under the name C. cyclicum, var. ampliatum Professor Nordstedt suggests to me that it should rather be a new species,

and certainly the number of small crenulations on the margin is about double that of Lundell's plant, which has only twelve. The rather widely-gaping constriction (from which I took my former name) seems to separate it from any species hitherto described.

Long., 51 μ; lat., 46–49 μ; crass., 16 μ.

Sumner Road, Lyttelton.

Cosmarium heliosporum, sp. nov. Plate III., fig. 30.

Frond small; segments in front-view sub-quadrate, crenate, with from ten to twelve conspicuous crenations; angles rounded; cytioderm marked with large granular inflations corresponding to the crenations and radiating from the median space, giving the frond a deeply-grooved appearance; in the median space, at the base of each segment, a row of small, apparently vertical inflations, usually five in each row. In side-view, segments sub-quadrate, slightly tapering to the wide ends, which are a little convex; edges smooth at the base of the segments, and minutely crenulate at the ends. End-view elliptical, with transverse rows of granules; viewed from the base of a segment the granules form a circle round the isthmus. Zygospore globose, with numerous spines; the spines subulate, on broad bases, and minutely divided at the apex.

Long., 28.3 μ; lat., 23 μ; crass., 15.6 μ; diam. zygosp. exclus. spin., 33 μ; long. spin., 3.5 μ.

Hawke's Bay.

A species belonging to the series of C. crenatum, but distinct by its sub-quadrate segments, which are conspicuously crenate at the ends, and by the form and size of the spines on the zygospore. From these spines Mr. Turner suggested to me the specific name which I have herein adopted.

*Cosmarium amplum, Nordstedt. Plate III., fig. 31.

I give a figure of this plant, partly because of its peculiar end-view in some cases (roundly triangular); partly because the granules seem to me often to be arranged in concentric curves, and not always in quincunx, as Professor Nordstedt reports; and partly on account of a conspicuous inflation, observed in some specimens when viewed neither in. front nor directly from the end. The plant is a fine one. Perhaps two-thirds of the specimens observed by me from Otaki have a triangular end-view; all those from Hawke's Bay have elliptical ends.

Hawke's Bay; Otaki.

Cosmarium quadrifarium, Lundell, var. gemmulatum, var. nov. Plate III., fig. 32.

Frond moderate; constriction deep, linear; segments in