554 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
In the mode of formation of the spores the species examined present 
considerable differences. The process which has been described as taking 
place in Cliondria tenuissima differs from that detailed above in several 
important particulars, especially in the wholesale conjugation before 
Spore-formation, and in the subsequent differentiation of a sporogenous 
portion from the resulting mass. 
Pleurocladia. — Prof. N. Wille* has investigated the structure of the 
freshwater alga Pleurocladia lacustris belonging to the Phasosporese. 
It has the appearance of a brown velvety coating on water-plants, each 
separate filament being enclosed in mucilage. The erect filaments 
spring from a basal disc, composed of primary filaments coalcscent into 
a pseudo-parenchymatous layer. Both kinds of sporange were observed, 
growing on the same individual ; the unilocular are pear-shaped, the 
plurilocular filiform ; the biciliated swarmspores escape from terminal 
openings ; both kinds of sporange are often proliferous. Long trichomes 
proceed from the erect filaments of the thallus, resembling those of the 
Ectocarpaceae ; the apical growth of these hairs soon ceases, their further 
elongation being effected by basal growth. The systematic position of 
Pleurocladia is clearly in the Ectocarpaceae near to Streblonema. 
Herr H. Klebahn f confirms, in essential points, the observations of 
Wille. Each cell of the vegetative filaments contains a parietal golden- 
brown chromophore, resembling in colour those of diatoms. The nucleus 
is minute, and is usually in contact with the cell- wall ; the cells of the 
hairs are colourless. The nearly ripe sporanges contain a large number 
of chromophores and nuclei. When mature the entire contents of the 
sporange assume an amoeba-like movement, and escape through the 
apical pore enclosed in mucilage. Each cell of the plurilocular spo- 
ranges produces only a single swarmspore, which is probably a gamete. 
The author was able to follow out the germination of the spores and the 
further development of the new individuals. 
Structure of Spirot8enia4 — Dr. J. Lutkemiiller has studied the 
structure of this genus of desmids, especially in relation to the spiral 
bands. He does not advocate the division of the genus into two ; but 
arranges the species in two sub-genera, in one of which the chlorophores 
are central or axile, in the other parietal; this classification nearly 
corresponds to that into species with one and species with more than 
one spiral band. Nine out of the 14 known species (including one new 
one) can be disposed of in this way, the others being either doubtful, or 
species in which the arrangement of the spiral bands has not been accu- 
rately described. The species of Spirotsenia show but little variation in 
the structure of the cell- wall or jelly ; in the mode of cell-division, which 
is oblique, in contrast to that of all other desmids ; or, as far as is known, 
in the formation of the zygotes. 
Development of the Sexual Organs of Vaucheria.§ — Prof. F. Olt- 
manns has followed out, in all its stages, the development of the 
antherids and oogones of several species of Vaucheria, especially V. cla- 
vata, fluitans, and aversa. The antherozoids agree with those of Volvox , 
* Ber. Deutsch. Bot. Gesell., xiii. (1895) pp. 106-12 (1 ph). 
f Tom. cit., pp. 93-106 (1 ph). 
i Oesterr. Bot. Zeitschr., xlv. (1895) pp. 1-6, 51-7, 88-94 (2 pis.). Cf. this 
Journal, 1894, p. 90. § Flora, lxxx. (1895) pp. 388-420 (5 pis.). 
