Fecundation in Orchidea and Asclepiadea. 715 



nally a granular appearance, which has been noticed though its 

 cause seems to have been overlooked. 



In the recent work of Meyen*, also, some examples of these 

 crystals in Orchideae are given. 



ASCLEPIADEA. 



The various statements and conjectures on the structure and 

 functions of the sexual organs in this family were collected, 

 and published in 1811, by the late Baron Jacquin, in a se- 

 parate volume, entitled, " Genitalia Asclepiadearum Contro- 

 versa." 



To this work, up to the period when it appeared, I may refer 

 for a complete history, and to the tenth volume of the Linnean 

 Society's Transactions, along with the first of the Wernerian 

 Natural History Society's Memoirs, published somewhat earlier, 

 for a slight sketch, of the subject. 



I shall here therefore only notice such statements as Jacquin 

 has either omitted or imperfectly given, and continue the history 

 to the present time. 



In 1763, Adanson correctly describes the stamina in Asclepias 

 as having their filaments united into a tube surrounding the 

 ovaria, their antherse bilocular and cohering with the base of 

 the stigma, and the pollen of each cell forming a mass composed 

 of confluent grains as in Orchideae. He is also correct in con- 

 sidering the pentagonal body as the stigma ; but he has entirely 

 overlooked its glands and processes, nor does he say anything 

 respecting the manner in which the pollen masses act upon or 

 communicate their fecundating matter to it. 



In 1779, Gleichen+j although he expressly says that in young 

 flower buds the pollen masses are distinct from those glands of 

 the pentagonal central body to which they afterwards are at- 



* Phytotomie. f Microscop. Entd. p. 73, et seq. 



tached, 



