235 
Life-History of Isoetes. 
no detailed account will be given here. The vegetative part 
of the prothallium is reduced to a single small cell cut off 
from one end of the spore ; the remainder of the spore forms 
the antheridium, as in Marsilia 1 . In the antheridium two 
walls are formed so inclined to each other as to include two 
upper cells and one lower. This latter next divides into two 
by a vertical wall, and subsequently by a periclinal wall is 
further divided into two peripheral and two central cells. 
Each of the latter divides once more, and each of the four 
central cells thus formed is the mother-cell of a spermatozoid. 
The full-grown antheridium thus consists of four peripheral 
and four central cells, and is therefore the most reduced 
among the pteridophytes. 
In many instances the microspores were imbedded with the 
macrospores, and as the nuclei could then be stained, the 
number of the peripheral cells, as well as the origin of the 
spermatozoids, was readily made out. The latter are too 
small in this species to be a good subject for the study of 
their development; but there is no doubt that, as in other 
cases, the body of the spermatozoid is derived mainly from 
the nucleus of the sperm-cell. At all stages it colours very 
intensely with gentian-violet, while the surrounding proto- 
plasm remains entirely colourless. Like the spermatozoids 
of the Filicineae, the body of the spermatozoid is spirally 
coiled, and multi-ciliate. Belajeff 2 , in a recent paper, opposes 
the generally accepted view that the body of the spermatozoid 
is of nuclear origin, and claims that only a small portion of it 
is derived from the nucleus. His views, however, are not 
supported by the recent work of Guignard on this subject, 
nor have I been able to find any confirmation of his state- 
ments from a careful study of a number of forms. 
1 Campbell, loc. cit., p. 341. 
2 Ueber Bau und Entwickl. d. Spermatozoiden bei den Gefasscryptogamen ; Ber, 
der Deutschen Bot. Gesellschaft, 1889, p. 122. 
