ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
77 
Pleurococce® ( Pleurococcus , Stichococcus, Scliizogonium, Prasiola ), Dacty- 
lococce® ( Dactylococcus , Rapliidium, Selenastrum, Actinastrum, Cruci- 
genia), and Gloeocyste® ( Geminella , Gloeocystis, Nephrocytium, Oocystis, 
Trocliiscia). There is no genetic connection between Pleurococcus and 
Stichococcus, nor between the various species of Scliizogonium and Prasiola. 
The alleged polymorphism of the lower Algae rests sometimes on inexact 
description of genera and species, sometimes on a simple external resem- 
blance, sometimes on an inaccurate interpretation. 
Chroolepidese.* — Herr G. Karsten gives a monograph of this family 
of Algae, comprising the genera Trentepolilia, Chroolepus, Phycopeltis, 
and Cephaleuros (including Mycoidea). Among the points of general 
structure described, he states that tho cell-wall varies in thickness 
according to the greater or less dryness of the habitat. The charac- 
teristic pigment of the cell-sap, hfematoclirome, which serves a purpose 
of protection to the other cell-contents, is specially described. The 
vegetative organs show a great variety in their degree of complexity ; 
the two first-named genera consisting of filaments, the two last-named of 
plates of cells. In the epiphyllous species of these two genera, each 
swarm-spore is transformed into an attachment-disc, which dovelopes 
into a large flat thallus. Tho swarmspores aro formed in two kinds of 
sporanges, globular and hooked, the latter being especially adapted for 
development in the air. Conjugation of swarmspores was observed by 
the author only in one species of Phycopeltis , and is believed by him not 
to be of a sexual character, since each of the two swarmspores is able to 
develope into a new individual without the assistance of the other. Five 
new species of Trentepolilia are described, two of Phycopeltis, and five of 
Cephaleuros, mostly from Java. 
New Prasiola. t — Under the name Prasiola japonica, Dr. E. Yatabo 
describes a new species which grows in rapid streams in mouutainous 
parts of Japan, attached to stones. It is collected in large quantities by 
the inhabitants, and used as an article of food in the same way as species 
of Ulva. 
Ccenogonium.J — M. P. Hariot holds that Ccenogonium dialeptum is a 
perfectly well-characterized alga. Sporanges have been found which 
by their structure recall certain species of Trentepolilia. Sometimes the 
primary cells of a lateral branch dilate and become ampulliform. In the 
mode of ramification and in the dimensions of the organs, C. dialeptum 
resembles C. simplex, and the author’s view is that these species ought 
to be united under the name Trentepolilia dialepta (Nyl.) Hariot. 
Furthermore he considers that C. diffractum ought to be T. dijfracta 
Har., and that C. effusum is identical with T. setifera Farl. ; while G. 
tenuissimum ought to bo ranged with C. dialeptizum Sirton. 
Actidesmium.§— Herr P. F. Eeinsch gives further details of the life- 
history of this very rare and remarkable genus of Protococcace®, which 
exhibits affinities, in different directions, with Pediastrum, Eydrodictyon, 
and Sciadium. In its earliest condition it consists of a free-swimming 
* Ann. Jard. Bot. Buitenzorg, x. (1891) pp. 1-66 (6 pis.). 
t Bot. Mag. (Tokyo), v. (1891) pp. 187-9 (1 pi.). 
X Journ. do Bot. (Morot), v. (1891) pp. 288-90. Cf. this Journal, 1890, p. 490. 
§ Flora, xlix. (1891) pp. 445-59 (2 pis.). 
