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



the figure shows only a slight difference in the form of the 

 prominences on the ridges. 



6. T. ARGUTA (Reinsch) Hansgirg, 1888, p. 129; Acantho- 

 coccus argutus Reinsch, 1886, p. 242, PL XII, figs. 19 and 23. 

 Cells solitary, globose, 31-43 p. diam., membrane very thick, up 

 to y$ the total cell diam., being 12-15 V-', ridges wavy, parallel, 

 or concentric, the projections subacute. 111. Europe. 



7. T. OBTUSA (Reinsch) Hansgirg, 1888, p. 130; Acantho- 

 coccus obtusus Reinsch, 1886, p. 243, PI. 'XII, fig. 21. Cells 

 solitary, globose, 34-37 /* diam., membrane T 6 cell diarn., with 

 parallel or concentric wavy ridges, waves obtuse. Mass. 



Europe . 

 3. CHLOROCHYTRIUM Cohn, 1874, p. 87. 



Cells rounded or irregular, with parietal chromatophore and 

 one or more pyrenoids ; asexual reproduction by akinetes, and 

 by biciliate zoospores with red stigma, formed by repeated 

 division, escaping singly or enclosed in a gelatinous mass ; 

 sexual reproduction by biciliate gametes similarly formed, leav- 

 ing the mother cell in a gelatinous mass, within which they 

 copulate, producing a 4-ciliate zygote, which finally penetrates 

 the tissue of the host plant, and there develops to the full size. 

 Marine and fresh water. 



KEY TO THE SPECIES OF CHLOROCHYTRIUM. 



i. In fresh water plants. 2. 



i. In marine plants. 3. 



2. A prolongation of the cell wall remaining where the zygote entered 



the host. i. C. Lemnae. 



2. Cell entirely enclosed, no prologation to surface of host. 



2. C. Knyanum. 



3. Cells with pointed base. 3. C. Schmitzii. 



3. Base of cell not pointed. 4. 



4. Cell subhemispherical, base flattened. 4. C. derinatocolax. 



4. Cells globose or subglobose. 5. C. inclusiim. 



i. C. LEMNAE Cohn, 1874, p. 87, PI. II; Klebs, 1881, p. 

 250, PI. Ill, figs. i-io. Endophytic in Lemna trisulca ; cells 

 ovoid, ellipsoid or irregular, up to ioo/xdiam.; sexual reproduc- 

 tion by biciliate .pyriform gametes, formed many in a cell, 

 escaping by the breaking of the cell wall, enclosed in a gelat- 

 inous vesicle, within which they conjugate ; the subspherical 

 zygote escaping and continuing active, germinating only when 

 falling on a frond of Lemna ; here attaching itself by the ciliate 

 end, and pushing a tubular extension in between two epidermis 

 cells of the host, the interior part expanding and the protoplasm 

 passing into it, and developing to the normal form and size ; 



