220 COLLECTING HAIRS [BOOK 11. 



M. Alphonse De Candolle is yet more explicit. He ex- 

 presses himself thus : " the arms of the style begin to diverge. 

 At the same time the pollen disappears, the collecting hairs 

 drop off, and the style becomes altogether smooth." Never- 

 theless, a microscopical examination of these hairs has satisfied 

 me that they do not fall off, but that they offer a phenomenon 

 of which I know no other example in the vegetable kingdom. 

 They are retractile, like the hairs of certain Annelids, or the 

 tentacula of snails. 



If we examine a thin longitudinal slice of a young style, 

 before the emission of the pollen, it is seen that these cylin- 

 drical hairs, a little tapering to their fine extremity, are formed 

 by an external lengthening of the epidermis, and that they 

 are perfectly simple, without articulation or partitions even at 

 their base. 



Immediately below the base of each hair, there exists in 

 the subjacent cellular tissue a cavity about equal in depth to 

 half or a third the length of the hair, continuous with its 

 cavity, and apparently filled with the same fluid. This cavity, 

 however, does not extend beyond the most superficial stratum 

 of the style or stigma, and has no relation to the tissues 

 situated deeper, of which mention will be made presently. 

 This arrangement is preserved up to the time of the expan- 

 sion of the flower, the hairs being at that time covered by 

 grains of pollen, applied over their surface, and held between 

 their interstices. 



But at this period the hairs retract into the cavities formed 

 at their base among the cellular tissue ; the terminal half 

 ensheaths itself in the half situated next the base, as it by 

 degrees returns into the cavity. The point only of the 

 hair remains projecting beyond the surface of the style, and 

 causes the asperities noticed by Cassini. Sometimes the hair, 

 in retracting thus within itself, draws with it a few grains of 

 pollen, which thus appear to penetrate the tissue of the style, 

 but which, in fact, are always on the outside of the hair. 

 With care these hairs may be pulled out again by the point 

 of a needle, and then the pollen-grains which appear to have 

 penetrated the style are immediately expelled. Such pollen- 

 grains undergo no change during their application to the 



