38 ERYTHEA. 



third of the vegetative filaments are rounded, 7-10// wide, one-half 

 to as long as broad, much more densely tilled with chromatophores 

 and food granules than the other cells. Those filaments which bear 

 the unilocular sporangia are one-third to one-half as long as those 

 that bear the plurilocular ones; the cells are 7-9// broad, two to 

 three times as long as broad, the cells of equal width throughout ; 

 the terminal cell is neither enlarged nor dark colored. Small 

 clusters of hairs are scattered through the filaments which are a 

 millimeter or so long and 6-9 /< broad ; the lower cells contain some 

 chromato[)h{)res and are twice as long as broad ; the upper cells are 

 two to eight times as long as broad. 



The terminal cell or cells of the shorter vegetative filaments 

 become transformed into large, very thick-walled unilocular spo- 

 rangia (PI. 1, Fig. 2, b & b'). The plurilocular sporangia are 

 formed by the transformation of the upper cells of the longer vege- 

 tative filaments (Figs. 4, 4', 4" & 4'"). The cells swell up, a par- 

 tition is formed at right angles to the filament, a second partition is 

 formed at right angles to the first, and the mother cell is thus divided 

 into four zoosporal cells. The emission of the zoospores was not 

 observed. The terminal cells apparently never form zoospores. 



The relationship of the plant is plainly with the Elachistace*. 

 The growth is apparently basal or sub-basal and the reproductive 

 organs are formed by the direct transformation of the vegetative cells. 

 The genus is in fact closely related to Leptonema of Reinke.* The 

 extreme thickness of the cell wall of the unilocular sporan- 

 gium might be taken as a suggestion that it, rather than the pluri- 

 locular sporangium, is the homologue of the oogone. 



Leptonema pasciculatum Reinke. For three successive 

 summers the writer collected small tufts of a light brown alga on 

 Postelsia palmoeformis Rupr. on all the rocky points where Postelsia 

 flourished and also from plants of the same species washed ashore at 

 various places along the Pacific Coast. Early in the season only 

 sterile material was collected, but late in August abundance of 

 material bearing plurilocular sporangia was obtained. Repeated 

 search for the unilocular sporangia has, however, been made in vain. 



*Atl. Deutch. Meeresalg. 13, tafl. 9-10. Engler u. Prantl, Pfl. Fam., 

 Lief. 86, p. 220, fig. 187. A-C 



