190 Mr. Brown on the Organs 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 Asclepiadez, the latter to Periplocee. 
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. 
Ín Asclepias 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. + Zeitsch. f.. Physiol. ii. p. 230. 
1829 
