EMBRYO-SAC Of GVMNADENIA CONOPSEA. 
17 
almost inconceivable. For if the Synergidte represent two 
cells of a protliallus, we may regard them possibly as 
remnants of the neck of an archegonium, and the egg- 
cell as its central cell ” (oosphere), and suppose that they 
have persisted in virtue of their use in reproduction. 
Strasburger says that one cell resulting from the division of 
the embryo-sac mother-cell becomes the embryo-sac, that 
its contents divide as described into eight nuclei by three 
divisions in alternating planes ; this embryo sac must be 
regarded as the macrospore — the equivalent of the embryo- 
sac of Gymnosperms. 
Looked at thus, the divisions in the embryo-sac represent 
a rudimentary prothallus, and the egg-cell^’ may be re- 
garded as the oosphere. The Synergidse were formerly 
thought to be the representatives of the canal-cell ; but 
Strasburger, who at first took this view, afterwards showed 
that since they are sister cells of the egg-cell, and 7iot a 
jyroduct of its division, such cannot be the case. He there- 
fore considers them and the antipodal cells,^^ as well as 
the nuclei which fuse to form the embryo-sac nucleus,’^ as 
merely seven cells of the prothallus. 
Strasburger, in criticising Vesque’s theory, points out 
that no stress can be laid on the fact that the division walls 
in the embryo-sac mother-cell are deliquescent ; for this, 
and the similar appearance in pollen-cells simply result 
from the imperfect nature of the process, since they will all 
be very soon absorbed, on the one hand by the* enlarging 
embryo- sac, on the other by the pollen grains. The same 
remark applies to the divisions in the temporary pro-embryo 
of Gymnadenia. 
Further, we cannot lay much stress on the tetrahedral 
arrangement of the nuclei, for the rule of rectangular 
division applies very widely,^ and in the history of Gymna- 
denia we have seen how the first divisions even in the 
embryo follow a similar order ; but in trichomes, prothalli, 
and other structures, the same obtains. 
But another view appears possible. It will be remem- 
bered that the first divisions across the embryo-sac mother- 
cell follow one another in such a way that the two cap- 
cells were spoken of as being cut off from the mother-cell 
by diffluent swollen Avails ; and that, the lower cell having 
enlarged, destroying the cap-cells, its protoplasm passes to 
each end and a vacuole-like clear space forms betAveen. 
This last division may probably be looked upon as merely 
’ See also Sachs, in ‘Wurzburg Arbeiteii,’ “Auordnung d. Zelleu in 
juugstcn Pflanzentheilen.” 
VOL. XX. NEW SER. 
