IN ORCHIDE^ AND ASCLEPIADEiE. 505 



of changes nearly agreeing with those which M. MirbeP 

 has described and illustrated as taking place in other 

 families. 



In the earliest state in which I have examined the ovulum 

 in Orchidese, it consists merely of a minute papilla pro- 

 jecting from the pulpy surface of the placenta. In the [708 

 next stage the annular rudiment of the future testa is 

 visible at the base of the papilhform nucleus. The sub- 

 sequent 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 ap- 

 proximate the apex of its nucleus to the surface of the 

 placenta, take place in ditferent 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 aUied, 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 Orchidese does not 

 materially differ from that of many other families. In the 

 early state the utriculi composing it are densely approxi- 

 mated, having no fluid interposed. In the more advanced 

 but unimpregnated 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 considers 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 



Annul, des Sc. Nat. xvii, p. 302 ; — and in Mm. de I'Acad. des So. de 

 I'Instit. ix, p. 212. 



