Fecundation in Orchidee and Asclepiadea. 703 
from the pulpy surface of the placenta. In the next stage the 
annular rudiment of the future testa is visible at the base of the 
papilliform nucleus. The subsequent changes, namely, the 
enlargement of the testa, the production of a funiculus, which 
is never vascular, and the curvature or inversion of the whole 
ovulum, so as to approximate the apex of its nucleus to the sur- 
face of the placenta, take place in different genera at different 
periods with relation to the development of the other parts of 
the flower. In general when the flower expands, the ovulum 
will be found in a state and direction proper for receiving the 
male influence. But in several cases, as in Cypripedium and 
Epipactis, genera which in many other respects are nearly 
allied, the ovulum has not completed its inversion, nor is the 
nucleus entirely covered by its testa until long after expansion, 
and even after the pollen has been acted on by the stigma, and 
its tubes have penetrated into the cavity of the ovarium. 
The tissue of the perfect stigmata in Orchidez does not 
materially differ from that of many other families. In the 
early state the utriculi composing it are densely approximated, 
having no fluid interposed. In the more advanced but unim- 
pregnated state, these utriculi enlarge, and are separated from 
each other by a copious and generally viscid secretion. The 
channel of the style, or stigma, whose parietes are similarly 
composed, undergoes the same changes. Both these states are 
represented in one of Mr. Dauer's plates, who however con- 
siders the more advanced stage as subsequent to impregnation. 
In the advanced but still unimpregnated state of the ovarium, 
the upper portions, which are in continuation with the axes of 
the three placenta, but do not produce ovula, are of a texture 
somewhat different from that of the greater part of the cavity, 
but still more obviously different from that of the cavity of the 
style, being neither apparently secreting nor consisting of 
VOL. XVI. 4x similar 
