Oogenesis & Embryogeny in Ephedra distachya. 169 
of nuclei is frequently found to occur in the jacket cell tissue ; cases 
are shown in Fig. 20 where the wall between two neighbouring cells 
has clearly broken down, and the nucleus from one is passing 
through the gap and fusing with that of the other. 
Mitotic division reappears at this stage among the jacket cell 
nuclei; it seems to result from the fusions of these nuclei, for in 
most cases, as in that represented in Fig. 21, a neighbouring cell 
could be found which is practically empty of contents, with the wall 
between them broken down. Also in this case forty-eight chromo¬ 
somes could be counted, i.e., twenty-four passing to each daughter- 
nucleus. This is the sporophyte number of chromosomes ; in other 
instances too, the larger sporophytic number appears to be present. 
Early in the history of the ovule when the jacket cells are being 
formed, twelve is the number present, agreeing with that found in 
the reduction and following divisions of the pollen mother-cells. 
It could not be determined what part this spindle formation 
plays in the development of the uninucleate pro-embryonal cells, 
but probably the latter are formed from the daughter-nuclei. 
Many of the jacket cells are at this time breaking up by a 
process of cleavage, their nuclei fragment, and cell walls grow in 
between the portions. A similar process is occurring in the 
archegonia, lines of cleavage appear in all directions in the cyto¬ 
plasm, which becomes very dense. This condition only lasts a short 
time; as soon as the suspensors have developed, and embryos are 
beginning to be formed at their tips, all the food material from this 
region has been absorbed and the archegonia and surrounding cells 
appear quite empty. 
A considerable number of these pro-embryonal cells break up 
in like manner eventually, particularly if they are some distance 
from the archegonia, and even of those close to and within the 
oospores, which put forth suspensors, comparatively few form 
embryos; the breaking up of the nucleus within some of them into 
a number of small nuclei again, as has occurred in Fig. 15 d, is 
probably the commencement of disorganization. 
Nevertheless, the power of these jacket cells to form pro- 
embryonal cells capable of giving rise to embryos cannot be doubted 
after an examination of these slides; thus we have here in the 
prothallium of a Gymnospermous plant a method of reproduction 
closely resembling that described by Messrs. Farmer and Moore 
and Miss Digby as occurring in certain so-called “apogamous” 
prothallia of ferns (10). In the case of Ephedra, however, the 
