Fecundation in OrchidecB and Asclepiadece. 731 



apparently additional part, not met with in other families ; the 

 second, the cohesion of the grains of pollen, and their applica- 

 tion in masses to the female organ. 



With regard to the first peculiarity it may be observed, that 

 there is no real addition made to the number of organs in either 

 family, and that in both families the apparent addition consists 

 in a modification or production of the stigma ; the modified 

 part of which loses the proper function of that organ. 



This production of the stigma, — which is generally present, 

 and wanting only in certain Orchideae, where its place is some- 

 times supplied by an analogous modification of the male organ, 

 — though differing very remarkably in appearance in the two 

 families, agrees in being originally distinct from the pollen 

 masses, and in the advanced stage becoming firmly attached to 

 them ; in adhering but slightly to the point of its formation 

 after the attachment to the pollen takes place ; and in being so 

 constructed as to be readily removed by insects from its original 

 position along with the pollen masses. 



As to the second point of agreement ; namely, the cohesion 

 of the grains of pollen into masses of considerable size, and the 

 application of these masses to the stigma, — it is obviously con- 

 nected with that which might perhaps be termed a third pecu- 

 liarity ; the apparent necessity for an unusual number of pollen 

 tubes which are to act in concert ; in the one family to penetrate 

 to and regularly arrange themselves in the cavity of the ova- 

 rium*; in the other, to open a communication with the stigma, 

 and then to pass along a non-secreting surface, until they arrive 

 at a distant point, where they are to be introduced into the 

 cavity or body of the style. 



With respect to the agency of Insects in fecundation in those 

 two orders, there can be no doubt that it is very frequently em- 

 ployed in Orchideae ; at the same time there are evidently cases 



* See Additional Observations. 



in 



