380 Excerpt a Botanica. 



XLVI. — Excerpta Botanica, or abridged Extracts translated 

 from the Foreign Journals, illustrative of, or connected tuith, 

 the Botany of Great Britain. By W. A. Leighton, Esq., 

 B.A., F.B.S.E., &c. 



No. I. On the Functions of the Hairs on the Stigma in the 

 Fecundation of the Campanulacece. By Adolphe Bron- 

 GNiABT. (Ann. des Sc. Nat. n. s. xii. 244.) 



The upper surface of the stigma of the Campanulas is, as has 

 been long known, clothed with long hairs, arranged in regular 

 longitudinal lines correspondent to the number and position 

 of the anthers, and especially visible in the flower-bud before 

 the emission of the pollen. The connexion between these hairs 

 and the pollen was first observed in many species of Campa- 

 nula by Conrad Sprengel, subsequently with greater care by 

 Cassini in Campanula rotundifolia, and has been since detected 

 by Alphonse DeCandolle in all the Campanulaceae, with the 

 exception of the small genus Petromarula. On the dehis- 

 cence of the anthers previously to the expansion of the co- 

 rolla, and whilst the stigmas continue still convergent, these 

 hairs are found covered with a considerable mass of pollen, 

 brushed as it were from the cells of the anthers. On the ex- 

 pansion of the corolla the stigmas separate and curve back- 

 wards, the anthers having shed their pollen wither away, the 

 pollen deposited on the exterior of the stigma becomes de- 

 tached, and the hairs disappear, leaving only slight asperities 

 visible on the surface of the stigma. According to Cassini 

 and DeCandolle these hairs are caducous. M. Adolphe 

 Brongniart by a microscopic examination proves that they are 

 not deciduous, but exhibit a phaenomenon quite unexampled in 

 the vegetable kingdom ; viz. that they are retractile, similarly 

 to the hairs of certain Annelides, or the tentacula of Snails. 

 A longitudinal section of the style previously to the emission 

 of the pollen shows these hairs to be cylindrical, slightly at- 

 tenuated at the apex, and formed by a prolongation of the ex- 

 ternal cuticle of the epidermis, perfectly simple, and destitute 

 of articulation or partition even at their base. Immediately 

 under the base of each hair, in the subjacent cellular tissue, 

 is a cavity equal in depth to one half or one third of the length 



