98 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



Under special conditions round or ovoid aplanospores may be 

 formed in large numbers in the root portions ; these aplanospores 

 may either produce zoospores, or grow directly into new plants. 

 After much confusion in regard to this genus, the studies of 

 Rostafinski and Woronin, 1877, appeared to settle the matter, 

 and since that time the genus has been considered as consisting 

 only of a single species, exceedingly polymorphous in its adapta- 

 tions to varying conditions. But the more recent investigations 

 of Klebs, 1896, and Iwanoff, 1898, show that apparently at least 

 three species must be distinguished, and one of these constitutes 

 a new genus, Protosiphon. The other two species continue in 

 Botrydium. There is no way of determining to which of these 

 three species any record of Botrydium granulatum may refer ; 

 but fortunately all three species are included in the material 

 distributed under that name in published American exsiccatae, 

 and can be described here ; few other localities than those of the 

 exsiccatae can be given, 



KEY TO THE SPECIES OF BOTRYDIUM. 

 i. Portion of cell above ground clavate with thin wall. 



i. B. granulatum. 

 i. Portion of cell above ground spherical with thick, stratified wall. 



2. B. Wallrothii. 



1. B. GRANULATUM (L,.) Greville, 1830, p. 196, PL XIX; 

 Rostafinski and Worouin, 1877, p. 16, in part, PI. I.; Wolle, 

 1887, p. 155, in part, PL CXXXI, figs. 1-9; P. B.-A.,No. 226. 

 Exposed portion 1-2 mm. diam., broadly clavate or obovoid, 

 with bright green contents and thin wall, tapering below to the 

 much branched subterranean portion ; zoospores formed in the 

 upper part, 10-20X5-8 n ; aplanospores formed in the lower por- 

 tion, globose or oblong, up to 50 /x diam. On moist ground, 

 especially clay ; probably generally distributed. Fig. 5. Mass., 

 N. Y., Cal. Europe, So. America, New Zealand. 



2. B. WALLROTHII Kiitzing, 1839, p. 387 ; B. granulatum 

 Rostafinski and Woronin, 1877, p. 16, in part, PL III, figs. 25- 

 28 ; Tilden, American Algae, No. 45, in part. 



Exposed portion globose, rarely equalling i mm. diam., with 

 dense, dark olive green contents and thick, much stratified 

 membrane, passing without transition into the narrow, cylindri- 

 cal underground portion, which for some distance is simple, 

 then branching relatively slightly ; the wall in the upper part of 

 this portion is so thick as almost to close the opening. On 

 moist ground. Minn. Europe. 



