520 ON THE OEGANS AND MODE OF FECUNDATION 



which, though probably originating with Richard in 1799/ 

 and briefly stated by him in 1802/ was first distinctly ex- 

 pressed as a conjecture in 1789 by M. de Jussieu. 



In 1817, Mr. Stephen Elliott states that he observed, in 

 his Todostigmd — a genus nearly allied to Asclepias — a 

 fibre or cord extending through the centre of the corpuscu- 

 lar pedicel or attenuated base of the stigma, and commu- 

 nicating from the anthera to the ovarium. He adds, that 

 Dr. Macbride has since seen it in some species of As- 

 clepias. 



There can be no doubt that the cord here noticed is of 

 the same nature with that which Gleichen has described in 

 a different state, and of which I shall presently have occa- 

 sion to speak. 



730] In 1824, Professor Link,* while he admits the distinct 

 origins of the pollen masses and glands or corpuscula 

 seated on the angles of the stigma, yet considers both these 

 parts as equally belonging to the anthera. In this respect 

 his opinion is identical with that of Gleichen. The pollen 

 mass, he adds, is composed either of a cellular tissue, or 

 manifestly of grains of pollen : the former part of the 

 description being no doubt meant to apply to true Ascle- 

 piadeae, the latter to Periplocese. 



Professor L. C. Treviranus, in 1827,' pubhshed some 

 observations on this family, in which his account of the 

 structure of the pollen differs in several points from that 

 exhibited in Mr. Bauer's drawings, vi'hich he states he had 

 seen three years before this publication. 



In Asclepias curassavica, the species more particularly 

 examined by Treviranus, he describes the pollen mass as 

 filled with compressed, nearly round but obtusely angular, 

 colourless, simple grains, containing minute granules ; the 

 pressure of the external grains, or those in contact with the 

 general covering, giving it the appearance of being cellular. 

 ; In speaking of the mode of impregnation, he says, that 

 the pollen mass, at the time when its connection is esta- 



' Mncycl. Boiaii. i, p. 213. = Bulliard, Lid. de Bot. ed. 2, p. 56 



3 Bat. of Carol, and Qeorg. i, p. 327. " FMl. Bot. p. 300. 

 ^ Zntsch.f. P.hyml. ii, p. 230. 



