94 VEGETABLE ORGANOGRAPHY. 



plusieurs tetes) ; these are branching filaments, each 

 branch of which is terminated by a httle glandular head, 

 as we see, for example, in Croton penicillatum. 



Under the general denomination of Excretory 

 Hairs, I comprehend the excreting canals of certain 

 glands : such are, for example, Stings, or Awl-sliaped 

 Hairs, fpili suhulati ; poils en aUne) ; or those the 

 gland of which is sessile upon the part which bears it, 

 and is prolonged into a tubular and sharp process, as we 

 see in the Nettle, (PL 3, C.) Of this kind, also, are the 

 Pili Malpighiacei ; Poils en navette (PI. 3, D), the glan- 

 dular base of which bears a horizontal hair, attached by 

 its centre, and tubular in the interior : through its two 

 extremities it gives passage to a fluid enclosed within 

 it ; this is what takes place in Malpighia urens. 



It is worthy of remark — 1st, that in all the glands 

 provided with excretory hairs, the fluid which they 

 secrete is of a caustic nature ; — 2d, that this fluid, which 

 never flows out naturally, is only directed to the outlet 

 which is prepared for it, when the gland, being pressed 

 by a foreign body, allows it to escape : it then follows 

 the course of the excretory canal, which, by its sharp 

 extremity, deposits it under the epidermis of the animal 

 which happens to touch it imprudently. This organiza- 

 tion is exactly analogous to the structure of the poison- 

 fangs of serpents. 



