690 Mr. Brown on the Organs and Mode of 



nion respecting the mode of impregnation agreed with that of 

 Batsch and Richard, thongh it is not there actually expressed, 

 nor indeed very clearly in another publication of nearly the 

 same date*, in which I had adverted to this family. But 

 I have since on several occasions more explicitly stated that 

 opinion, which, until lately, I always considered the most pro- 

 bable hypothesis on the subject. At the same time its probabi- 

 lity in this family appeared to me somewhat less than in Ascle- 

 piadeae. For in Orchideae a secreting surface in the female 

 organ, apparently destined to act on the pollen without the in- 

 tervention of any other part, is manifest ; and some direct evi- 

 dence of the fact existed, though not then considered satisfactory. 

 In Asclepiadeae, however, I entertained hardly any doubt on the 

 subject ; the only apparently secreting surface of the stigma in 

 that family being occupied by the supposed conductors of the 

 male influence, and no evidence whatever, with which I was 

 acquainted, existing of its action through any other channel. 



In 1816 or 1818 I received from the late celebrated Aubert 

 du Petit Thenars some printed sheets of an intended work on 

 Orchideae, which, with a few alterations, was completed and 

 published in 1822+. 



From the unfinished work, as well as that which was after- 

 wards published, it appears that this ingenious botanist con- 

 sidered the glutinous substance connecting the grains or lobules 

 of pollen as the "aura seminalis" or fecundating matter; that 

 the elastic pedicel of the pollen mass, existing in part of the 

 family, but according to him not formed before expansion, 

 consists of this gluten ; and that in the expanded flower the 

 gluten which has escaped from the pollen is, in all cases, in 

 communication with the stigma, 



He describes the stigma as forming on the surface of the 



* Linn. Soc. Transact, x. p. 19. f Hist, des Orchid, p. 14. 



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