110 



THE AMERICAN MONTHLY 



[June, 



are produced from the chlorophyllous 

 contents, which escape through tubu- 

 hir projections, either into intercelhdar 

 space or the surrounding water. Rest- 

 ing cells with thick walls have been 

 observed. 



[These plants have been found in 

 Lem)ia and Ceratophylhuu. They 

 have not been observed in this covni- 

 try.] 



34. Genus Characium A. Braun. 



Cells always with one end attached, 

 usuallv with a pedicel, of various 

 forms. Propagation by zoospores 

 formed by successive binary division 

 within the mother-cells, escaping 

 singly through a lateral opening in 

 the cell-wall. 



[The cell-contents are homoge- 

 neous or granular, finally breaking 

 up into numerous oblong zoospores 

 with two cilia, which fill the cell. 

 When they escape they make their 

 wav to some plant in the water to 

 which thev become attached and grow 

 into new plants like the parent. 



The Genus Hvdi-ocvtiiim A. 

 Braun seems not to difter in any way 

 from Characeiini, and we have, 

 therefore, omitted it. Rabenhorst 

 describes a peculiar stellate arrange- 

 ment of the zoogonidia, in which a 

 number of the motile cells are united 

 together bv their ends in a radiate 

 manner.] 



3=5. Genus //iv/r/rt' ;///■/;/ Rabenhorst 



Cells as in CJiaraciiini^ but contents 

 at first homogeneous, afterwards con- 

 tracted into an ovoid green body, froin 

 which, by oblique division, 2-4-8 

 short zoogonidia are produced, each 

 with two cilia, which escape by a 

 terminal aperture. 



[This genus may well be included 

 under Characitim.~\ 



36. Genus Codiolum A. Braun. 



Young cells obovate, later cylin- 

 drico-subclavate, stiptate, aggregated 

 in tufts ; contents green, finely granu- 

 lar, with numerous starch-granules. 



Propagation by zoospores and rest- 

 ing spores (hypno spores.) 



[This genus is found in both fresh 

 and salt water.] 



37. Genus Op/iiocytium Nageli. 



Cells cylindrical, straight or vari- 

 ously curved, usually one end attenu- 

 ated to a short. stem, contents green, 

 usuallv with red or reddish-yellow 

 spots . 



Propagation by zoospores formed 

 by the simultaneous subdivision of 

 the contents, which pass out and be- 

 come distributed. 



[The curved forms of the older 

 cells enable this genus to be readily 

 recognized. The young cells are 

 short, and often attached. Later they 

 become much curved in half-circles, 

 or s shaped.] 



Ik Pseudoccenobia. 



38. Genus SciadiKm A. Braun. 

 Family of cylindrical or so'mewhat 



curved cells, united by short stems ; 

 on the ends of the older cells the 

 daughter-cells stand fan-like, and this 

 arrangement is repeated with the 

 daughter-cells, making a tree-like 

 growth. 



Propagation by elongated z o o - 

 spores, formed b}- division of the con- 

 tents, usually into six parts, which 

 escape through the end of the cell, 

 the top being thrown oft' like a lid. 

 They become attached at the summit 

 of the cell, and there grow, produc- 

 ing the characteristic form of the 

 plant. 



[The intimate connection between 

 this genus and Ophiocytimn will be 

 readily seen. In one case the zoo- 

 spores separate, in the other they 

 grow together about the end of the 

 mother-cell.] 



C. CcENOBI^. 



39. Genus Scenedcsnnis Meyen. 

 Cells elongate, polymorphous, often 



with spine-like projections at the ends, 

 joined by their sides in series of 2-8. 



Propagation by gonidia formed by 

 division of the contents of a mother- 

 cell. These arrange themselves within 

 the latter in the form of a new ccpno- 

 bium. 



[A very common genus, of con- 

 siderable interest from its close rela- 

 lion to Hydrodictyon in regard to 



