* 



ZOOLOGY AND BOTAI^Y, MICROSCOPY, ETC. 75 



bushy, 5 to 10 cm. high, and disposed fairly regularly ; they often form 

 small loose bundles, resembling locks of hair. These upright filaments 

 emerge from a creeping substratum which grows on the slime, and is 

 ■composed of entangled rhizomatoid filaments. It is at the expense of 

 the creeping part that the tubercles are developed which play so great a 

 part in the multiplication of the plant. The rhizomatoid filaments 

 produce here and there irregular swellings provided with papillte, some 

 of which develop into new green shoots and others into rhizomatoid 

 filaments. These latter are capable of producing in their turn new 

 swellings, and so on. Thus the plant is able to spread over large 

 surfaces, and the thallus of separate plants becomes intermixed. The 

 author found plants bearing the sexual organs which have seldom been 

 observed, and only once previously in Europe, under natural conditions. 

 They are sufficiently rare when they do occur, and a search of several 

 square decimetres barely produced ten, while the same material fur- 

 nished easily more than a hundred tubercles. The oospores apparently 

 remain inside the oogonia, and the latter adhere for several months' to 

 the individuals which produce them. It is evident that multiplication 

 by means of the tubercles and the rhizomatoid filaments is very much 

 more usual than sexual reproduction, and is possibly in course of taking 

 its place. In D. pusillus, described by Collins, sexual organs have not 

 been found. As regards the structure of the cells, the author finds that 

 Mirande alone of previous writers is correct in his conclusions. The 

 membrane is constituted like that of the Udotefe, and consists of a 

 callus associated with pectic components. The author proposes in a 

 further work to discuss the germination of the oospores. 



Nuclear Division in Characese.'- — F. Oehlkers discusses nuclear 

 division in Characeai. Tlie number of chromosomes in C. fragiUs is 

 twenty-four, in C. fcetida sixteen, and in NiteJla syncarpa twelve. hX 

 the germination of the zygote of C. fcBtida, the zygote nucleus divides 

 into two daughter-nuclei, which then undergo further division. Of the 

 three transverse walls, two are dissolved, while the third, which separates 

 off the fourth nucleus in a protoplasmic cup, remains. Only this last 

 nucleus survives, while the other three gradually go to pieces. This 

 fourth nucleus divides into two by a wall parallel to the longitudinal 

 axis of the zygote. Through further divisions of these two cells, two 

 knobs are formed above the first transverse wall, and these are the point 

 of issue of the new Chara plant. The number of the chromosomes 

 in the second division was sixteen, the same as that of the vegetative 

 division. Reduction-division takes place, therefore, at the actual germi- 

 nation of the zvffote. 



'to^ 



Alternation of Generations in Florideae.t — N. Svedelius discusses 

 the problem of the alternation of generations in Florideae. The signifi- 

 cance of the reductions-division does not lie entirely in the restoration 



* Ber. Deutsch. Bot. Gesell., xxsiv. (1916) pp. 223-7. See also Bot. Centralbl. 

 cxxxiv. (1917) p. 279. 



t Naturw. Wochenschr., n.f. xv. (1916) pp. 353-9, 372-9. See also Bot. Cen- 

 tralbl., cxxxiv. (1917) pp. 314-5. 



