Excerpta Botanica. 381 



of the hair continuous with the cavity of the hair itself, and 

 to all appearance filled with the same fluid. This basal cavity- 

 does not extend beyond the superficial layer of the stigma, 

 and has no connexion whatever with the tissue which lies at a 

 greater depth. 



On the expansion of the corolla, these hairs, which had be- 

 fore continued extended and covered with grains of pollen, 

 retreat into the basal cavity in the cellular tissue, their ter- 

 minal portion insheathing itself in the lower portion gradually 

 as this lower portion itself retires into the basal cavity in the cel- 

 lular tissue, until the apices alone of the hairs remain slightly 

 projecting from the external surface of the stigma. In their 

 retreat the hairs frequently draw along with them some grains 

 of pollen, which apparently penetrate into the tissue of the 

 style, but which in reality remain always in contact with the 

 exterior surface of the hairs, as is clearly proved by applying 

 the point of a needle and causing the hairs to reissue from 

 their insheathment, when the pollen grains are instantaneously 

 expelled. The pollen grains undergo no modification either 

 during their application to the hairs or when drawn along with 

 them in their retractile movement, and consequently no con- 

 nexion exists between them and the interior of the style. The 

 probable cause of this retractile movement Brongniart attri- 

 butes to the absorption of the fluid contained both in the hair 

 and in the cavity at its base. 



Cassini, A. DeCandoUe, Treviranus, and Link are of opi- 

 nion that fecundation is effected by the action of the pollen 

 on these hairs, but in Brongniart's estimation erroneously. 

 For on dissecting the true stigmas of the Campanulas, viz. the 

 internal surface of the stigmatic branches, afler their diver- 

 gence, the pollen grains are found dispersed on this surface 

 and adhering to it as on all true stigmas, at first by the lubri- 

 cating moisture of the part, and subsequently by the develop- 

 ment and penetration of the pollen-tubes, which very soon 

 extend into a bundle of fine elongated utricular tissue occu- 

 pying the centre of the style. This tissue is in form hexagonal, 

 perfectly distinct from the surrounding tissue, much -denser, 

 and coloured. Its separation is easily effected when it is found 

 composed of cylindrical or slightly fusiform elongated utri- 



