96 VEGETABLE ORGANOGRAPHY. 



pointed out the terms by which they are designated ; 

 but it is now proper to consider them with regard to 

 Organography. The principal differences of form which 

 deserve to be mentioned, are the following: — 



1st. Simple Hairs, (PL S, E,) or those formed by the 

 elongation of a single cellule ; they have, consequently, 

 no division inside, or ramification: these are the most 

 frequent of all in the vegetable kingdom, and are com- 

 monly cylindrico-conical, or conical, and very variable 

 in their length, consistence, direction, and number. 



2d. Divided f cloisonnes) Hairs, (PI. 3, F,) or those 

 formed of several cellules placed end to end in a single 

 row, and separated by partitions more or less visible : 

 they often have the name of Articulated Hairs given to 

 them — a term evidently incorrect, since there is not in 

 any of them any kind of articulation, or natural point of 

 separation. They may be distinguished according as 

 they present a cylindrical or conical appearance, which 

 takes place when the cellules are not swollen up; or 

 rough and strangulated, or moniliform, (PI. 3, G,) which 

 is due to the cellules being often swollen out between 

 the partitions, whence results their necklace-like ap- 

 pearance. 



3d. Branched (rameux) Hairs are formed of several 

 cellules, which, instead of being placed end to end, 

 diverge in different directions. We know that these 

 modes of ramifications can vary much without the nature 

 of the hair being much altered : it is here that we class 

 the forked or Y-shaped hairs of Alyssum ; the trifurcated 

 or trifid ones of several Cruciferas ; the dichotomous ones 

 of some Cruciferae ; the Pili Malpighiacii, (poils en 

 navette,) or those which, divided at their base into two 

 branches, spread upon the surface of the leaf, and 

 directed in a single line, seem Hke little shuttles placed 

 horizontally, as is seen in Astragalus asper ; those 



