1885.J 



MICROSCOFICAL JOURNAL. 



109 



Cells like Characeum^ contents con- 

 tracted into a ball. 



Hydrianum^ 35. 

 Cells stiptute, in tufts. Codiolum, 36. 

 Cells cylindrical, curved, free. 



Ophiocytium^ 37. 



b. Individual cells united in a coeno- 

 bium-like family, which, however, dif- 

 fers from a true ccenobium, in that their 

 cells are not all of one and the same 

 <:^eneration. Zoospores by simulta- 

 neous division. (Pseudoccenobi^.) 



Synopsis of Genera. 

 l'21onuate cells, spreading from end of 

 mother-cell, forming tree-like fomi- 

 lies. Sciad/um, 38. 



c. Individual cells united in coeno- 

 bia, or families of definite form, pro- 

 duced by the growth of daughter-cells 

 of. one and the same mother-cell. 

 These plants differ from the multi- 

 cellular algae in that the single cells 

 show no vegetative division. (Cceno- 



BI^E.) 



Synopsis of Genera. 

 Elongate cells in series of 2-8 side by- 

 side. Scenedesmus., 39. 

 Ccenobium globose, solid ; cells angu- 

 lar, tw'o spines at angles. 



Sorastrum^ 40. 

 Cells half-moon shaped, convex mar- 

 gins joined in coenobia of 4-8. 



Se/enastrum, 41. 



Ccenobium spherical, hollow, cells in 



a single reticulate layer near the 



surface. Coelastrum. 42. 



Ccenobium flat, round or oval. 



Pediastrum ., 43. 

 Ccenobium a net, formed of cylindri- 

 cal cells placed end to end forming 

 the meshes. Hydrodictyon., 44. 

 Genus of doubtful value omitted 

 (combined with Characeum.T,^): — 

 Hydrocytium. 

 a. Eremobi.e. 

 31. Genus Po/yedrium i>ia.ge\i. 

 Cells single, angular, free swim- 

 ming, tliree or more angled, the cor- 

 ners lying in one plane, or tetrahe- 

 dral ; contents chlorophyll - green , 

 often with red spots. 



Propagation by gonidia, 3-4 form- 



ing of the contents of one mother-cell, 

 which pass out through an opening 

 in the wall, covered with a delicate 

 envelope and grow separately. 



Apparently some of the species 

 here placed belong in the develop- 

 ment-cycle of camobian protococca- 

 ceae, and correspond to the so-named 

 polyedern of Hydrodictyon observed 

 by Pringsheim, from which, by free 

 cell formation, new hydrodictyon- 

 nets develop. 



[Some of the forms bear close re- 

 semblance to certain desmids, especi- 

 ally to members of the large genus 

 Staurastrum. Their mode of pro- 

 pagation is quite different.] 



32. Genus Protococcus Agardh. 



Cells spherical, not attached, sin- 

 gle or in irregular masses, with green 

 or red contents, a starch granule and 

 vacuole. Zoospores formed by suc- 

 cessive binary division. 



[The appearance of Protococcus is 

 so very much dependent upon condi- 

 tions, that it is not possible here to 

 describe its many transformations. 

 When in the water the cells may be 

 actively swimming about, but most 

 frequently it will be recognized as a 

 thin, powdery layer of cells, or, in 

 the presence of abundant moisture, 

 the cells may be surrounded by gela- 

 tinous envelopes. It occurs on bark 

 of trees, damp walls, etc.. and seems 

 to be not unfrequently confounded 

 with Pleurococcus ^ which is found in 

 similar places. It is, indeed, doubt- 

 ful if the two genera are distinct, al- 

 though Pleurococciis is seldom ob- 

 served except in the vegetative con- 

 dition, while Protococcus is more 

 ready to pass into the motile condi- 

 tion in the presence of water. 



It is more than probable that many 

 of the plants included in this genus 

 belong to the life-cycles of higher 

 algae.] 



33. Genus Chlorochytrium Cohn. 

 Endophytic plant. Cells spherical, 



oval, kidney-shape, or 2- 3- multi- 

 lobed, single or in groups in the in- 

 tercellular space of the parenchyma 

 of water-plants. Numerous Koospores 



