2 
H. MARSHALL WARD. 
had been recognised by Hofmeister as the homologue of a true 
prothallium.i It was also generally admitted that the endo- 
sperm of Angiosperms had nothing to do with that of Coni- 
fers, but rather corresponds to what is found appearing late 
in the developing macrospore of Selaginella, and independent 
of the prothallium.2 
Quite lately the necessity for a reconsideration of these 
points has been forced upon us by the researches of Stras- 
burger,^ of Warming/ and the papers of Vesque/ which 
clearly showed that in a great number of types the embryo- 
sac does not arise so simply as Hofmeister thought, and 
further, that the processes going on between its formation 
and the origin of an embryo are still more complex. 
Before touching upon this or examining the different 
views of the authors named, I propose to state what is found 
to occur in Gymnadenia conopsea^ one of the commoner 
Orchids of Europe. This has been partly done by Stras- 
burger,® who has, however, more especially described the 
processes in Orchis pollens and Monotropa hypopitys. The 
later stages have not, to my knowledge, been before de- 
scribed. 
Except where stated otherwise, the method employed has 
been to cut sections of the ovaries which have lain in abso- 
lute alcohol at least twenty-four hours, and in a slowly 
evaporating mixture of alcohol and glycerin at least twenty- 
four hours longer. In a few cases staining with fuchsine 
and acetic acid has been resorted to successfully. As is 
well known, the ovules arise from three parietal placentae, 
as outgrow^ths of a few cells projecting into the cavity 
of the inferior ovary. Hofmeister traced the Orchid ovule to 
one cell of the surface, whence arose the idea that it is 
morphologically a trichome."^ 
At a period shortly before the flower bud is complete, trans- 
verse sections of the ovary reveal the young ovules as straight 
or very slightly curved structures, arising in considerable 
numbers from each placenta and directed at right angles to 
its surface. Each consists of an axial row of large polygonal 
cells, surrounded by one layer of somewhat smaller cells. In 
transverse section we see one large cell with five or six 
^ Loc. cit. 
2 Cf. also Sachs’ ‘ Text Book,’ Eng. Trans. 
^ *Ueber Befrucbtuug und Zelltlieiluug,’ 1877. 
“ ‘Ann. d. Sc. Mat. Bot.,’ 1878. 
^ Ibid. 
® Op. cit., and ‘ Die Gymnosp. und Angiosp,’ 1879. 
^ ‘ Cf. also Sachs’ * Lehrbuch.* 
