THE HAIRS. lot 



however, that the general theory can be but little 

 doubted. 



The diversity of form in hairs, which is sometimes 

 met with upon the same surface, is probably connected 

 with their different uses: thus it is possible that some 

 serve as a defence against insects, and others against wet, 

 or the too intense action of the light. 



The difference in hardness ought probably to be also 

 assigned to the same cause : thus there are some hairs 

 which are destroyed or fall off early ; such are those of 

 the buds of which I have before spoken, and which are 

 destined to protect the young shoots from cold and 

 damp. In general, the hairs spring from the veins of 

 stems or leaves at the time of their first development ; 

 whence it results, that, by the gradual increase in size 

 of these organs, the hairs have a tendency to separate 

 from one another, without their total number however 

 being diminished: thus it is not rare to see leaves or 

 ovaries, which in their infancy are entirely covered with 

 very thick-set hairs, appear in their adult state only to 

 have a small number, because the increase of the surface 

 in all directions has caused them to separate from one 

 another. The reverse phenomenon is also met with, 

 though very rarely. I have already spoken of the hairs 

 which are developed in the calyx of the Labiatae after 

 flowering ; there is another curious example of this late 

 development of them, which has been pointed out to 

 me by M. Deleuze : the panicle of the Sumach (Rhus 

 cotinus) is almost entirely smooth during flowering; after 

 this period, those pedicel wliich bear fruit still remain 

 smooth or scarcely pubescent, whilst those the fruit of 

 which is abortive (and this happens in the greatest 

 number) have a considerable quantity of hairs developed 

 on them, so as to give them a bristly appearance, whence 

 gardeners have given this shrub the name of the Arhre 



