Fecundation in Orchidece 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 Orchideae 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. Bauer'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 placentae, 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. 4 X similar 



