PHZOPHYCE® 117 
they cease first at the apex, which becomes hyaline 
and elongate, and eventually continue only in 
places here and there. The filaments, simple or 
branched, are for the most part of one single cell- 
row and rarely divided by longitudinal walls. Some- 
times the cells of the erect filaments produce rhizoids 
which descending form a loose weft about the shoot. 
Where a basal horizontal layer occurs (¢.g., Ascocyclus 
and Phycocelis) it grows by peripheral cell-divisions 
and bears on its upper surface sporangia, hairs and 
paraphyses. 
The Reproductive Organs.—The plurilocular spor- 
angia, which may be of one or more rows of loculi, are 
formed either by the differentiation of the upper por- 
tion of a branch or an intercalary part of it; or they 
are definite outgrowths of cells of the erect filaments 
or primary basal layer. In Sorocarpus they occur in 
dense clusters; but in the other genera they are free 
like the branches and mostly elongate, cylindrical, or 
oval in shape. They are commonly of several rows - 
of loculi, but sometimes of a single row, wholly or in 
part. The gametes escape from all the loculi usually 
by an apical or lateral opening, and their conjuga- 
tion is of a peculiar character. In Ectocarpus silicu- 
losws, in which it has been carefully observed, the 9 
gamete first comes to rest and is then surrounded by 
numerous ¢ gametes, one of which succeeds in con- 
jugating with the 9 gamete. That the ? gamete 
should first come to rest before becoming susceptible 
of conjugation recalls the case of Cutleria, and also 
in part that of Myrtotrichia. The occurrence of 
bodies which can only be termed antheridia in 
