156 University of California Puhlicaiions in Botany [Vol.6 



become fertile. They increase considerably in thickness, measuring 

 21-33/A across. The short branches, first the upper (older), then grad- 

 ually the lower (younger), are transformed, at the same rate and 

 in the same manner, to unbroken chains of sporangia ; they appear 

 slightly club-shaped (pi. 19, figs. 4, 5). Only the basal cell remains 

 sterile, and the mother-cell of a pair of branches never seems to form 

 spores ; sometimes one or two cells above and below also are sterile. 

 Each full-grown cell gives rise to 32 or 64 zoospores, about 4-5|it across. 



The reason why Saunders regarded this plant as conspecific with 

 Reinke's Leptonema was that, in both, the upper part of large erect 

 threads are transformed into plurilocular sporangia. But he empha- 

 sized the fact that unilocular sporangia — being basal in Leptonema 

 as in other Elachistaceae — must be discovered before the identity can 

 be proved. However, even if such organs were found, making it 

 possible to regard the plant as a Leptonema, it is not identical with 

 L. fasciculatum, nor with any other known species of that genus. The 

 process in the formation of sporangia is different in the two cases, 

 and the ramification of the long filaments has no correspondence at 

 all in Leptonema. And even if the mode of growth is about the same, 

 it does not happen here, as in Leptonema, that the vegetative divisions 

 soon become localized in the basal zone ; only when, in our plant, the 

 entire upper parts have become fertile there remains only the basal 

 zone where cell divisions can take place. 



We cannot include our plant within the same family as Leptonema. 

 Its characters speak entirely in favor of the Ectocarpaceae, with 

 Ectocarpus, Strehlonema and FylaieUa. Those authors who regard 

 the latter genera as sections or subgenera of Ectocarpus in a wider 

 sense would probably not hesitate to bring our species to that same 

 genus. It is of course not possible to bring it to Euectocarpus, in 

 spite of the fact that plurilocular sporangia sometimes, though only 

 very occasionally, are formed by a series of cells in the filaments, 

 which otherwise always remain sterile, e.g., in E. tomentosns (Huds.) 

 Lyngb. (see Boergesen, Marine algae of the Faeroes, Copenh.. 1902, 

 p. 414, fig. 43). AVe have as little reason to compare it with Strehlo- 

 nema, even if we include E. tomentosoides Farl. For, in spite of the 

 " Phycocelis-stage " of this species (see Kuckuck, Ueber Polymorphic 

 hei einigen Phaeosporeen, Festschrift fiir Schwendener, Berlin, 1899), 

 the lateral, "ectocarpoid" sporangia is the typical type in Strehlonema. 



So far as the author is able to judge, there are, however, no serious 

 obstacles against bringing our plant to Pylaiella, as a new species. 



