Classification, 155 



Distingnished by the two superposed cells, the 

 lower sterile and producing rhizoids, the upper 

 fertile. 



Rhizidmm intestinum, Schenck. 



Zoo sporangium globose, 35-40 yu, diameter, either 

 external or immersed in the matrix, in the latter case 

 a beak is develop ed which pierces the cell-wall of the 

 host and through which the zoogonldia escape, zoo- 

 gonidia subglobose, with one long cilium; basal cell 

 small, 5-7 ^ diameter, either superficial or immersed 

 in the host, furnished with a few elongated rhizoids, 

 2-3 /^ thick. 



Rhizidium intestinum, Schenck, Ueb. Vork. Zell. 

 pi. Zopf. zur Kennt. Phycom. p. 51, t, 8, figs. 1 — 15; 

 iSacc. Syll. vii. 1, n. 1024. 



On species of Chara and Nitella. Rare. 



Bhizidium Westii, Mass. (n. sp.) (figs. 36, 37). 



Zoosporangium spherico-depressed, superficial, 20- 

 25 //< diameter, sterile basal cell immersed in the 

 host, subglobose, 6-10 yu, diameter, furnished at the 

 base with a few slender, branched rhizoids; zoo- 

 gonidia broadly pyriform, 4x3 /jl, furnished at the 

 thin end with a very slender cilium, 20-25 filong. 



Gregarious on Spirogyra nitida and Cladoplwra 

 gloTiierata. Not uncommon. 



When parasitic on a thin- walled host, as Spirorjijra, 

 the zoosporangium is sessile on the lower sterile cell, 

 but when parasitic on Cladopliora, where the cell-wall 

 is thick and laminated, the sterile cell is situated 

 within the innermost layer of the wall, and at the 

 period of reproduction emits from its apex a thin 



