720 Mr. Brown on the Orga7is and Mode of 



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 iden- 

 tical 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 Asclepiadeae, the latter to Periploceae. 



Professor L. C. Treviranus in 1827+ published some obser- 

 vations 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, which he states he had seen three years 

 before this publication. 



In Asdepias curassavica, the species more particularly ex- 

 amined 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 connexion is established with 

 the process or arm of the gland, which is then very viscid, 

 undergoes manifest changes, from being ventricose and opake 

 becoming flat, hard, and transparent. These changes he thinks 

 are probably owing to the extraction of its fecundating matter 

 by the process through which it passes to the glands, and by 

 them to the angles of the stigma, whence it may be easily com- 

 municated to the styles and ovaria. His opinion, therefore, in 

 every respect agrees with that which originated with Richard 

 and Jussieu, and which I had adopted. 



The celebrated traveller and naturalist. Dr. Ehrenberg, in 



* Phil. Bot. p. 300. t Zeitsch.f. Physiol, ii. p. 230. 



1829 



