MUL TINUCLEA T^E 285 



LITERATURE. 



Thuret Ann. Sc. Nat. (Bot.), xiv., 1850, p. 214. 

 Pringsheim Member. Akad. Berlin, 1856, p. 225 (Quart. Journ. Micros. Sc., 1856, 



p. 63). 



Schenk Wurzburg Verhandl., viii., 1858, p. 235. 

 "Walz Pringsheim's Jahrb. wiss. Bot., 1866, p. 127. 

 Solms-Laubach Bot. Zeit., 1867, p. 361. 

 AVoronin- Bot. Zeit., 1869, p. 137 et seq. 

 Nordstedt Bot. Notiser, 1878, p. 176; and 1879, p. 177 ; and Scottish Naturalist, 



1886. 

 Stahl Bot. Zeit., 1879, p. 129. 



ORDER 2. BOTRYDIACE^E. 



This order consists at present of only a single genus, Botryditim Wallr., 

 represented by the single species B. granulatum (Wallr.), differing widely 

 from Vaucheria in its mode of reproduction. This remarkable organism 

 forms minute green blobs on wet clayey ground or in dried-up pools, and 

 is attached to the soil by branching root-like rhizoids. The young plant 

 consists of a single nearly spherical cell, branched hyaline prolongations 

 of which constitute the rhizoids, while in the upper swollen part the proto- 

 plasm forms a hyaline parietal layer containing chlorophyll. From this 

 protoplasm are ultimately produced a number of zoospores, each pro- 

 vided with only a single cilium, which germinate directly on the damp 

 soil after becoming invested with a double cell-wall of cellulose. If the 

 zoosporange is exposed to drought, the vesicular portion shrivels up and 

 the chlorophyll is driven into the underground portion, which then divides 

 into a number of green cells. These may germinate in three different 

 ways: (i) Each cell becomes an underground zoosporange, producing 

 zoospores of the ordinary kind ; or (2) each cell may develop into an 

 ordinary vegetative plant; or (3) each cell becomes a hypnosporange, 

 closely resembling the ordinary vegetative plant, with a vesicular portion 

 above the surface, and hyaline rhizoids, but of an olive-green colour; 

 these may retain their vitality for a whole year and then produce zoo- 

 spores. The ordinary vegetative plant may also, under certain con- 

 ditions, break up into a number of resting-spores, of a brownish red 

 colour, which have been described as species of Protococcus. These 

 may either give birth to zoospores of the ordinary kind or to biciliated 

 zoogametes which conjugate in pairs, or sometimes in larger numbers. 

 The resulting zygosperm ('isospore' of Ros*tafinski) soon rounds itself 



off and germinates. 



LITERATURE. 



Janczewski et Rostafinski Mem. Soc. Sc. Nat. Cherbourg, 1874, p. 273. 

 Janczewski u. Woronin Bot. Zeit., 1877, p. 649 et seq. 



