CHAP. II. 
HAIRS. 
47 
surface, and diverge a litde from dieir centre, as in the Mal- 
low tribe. It is hairs of this description that close up the 
abortive stomates upon the under side of the leaves of Dionaea 
muscipula. 
Hairs are either formed of a single cell of cellular tissue 
(Plate I. fig. 8. Z>), or of several placed end to end in a single 
series (Plate I. fig. a, b.), whence, if viewed externally, they 
have the appearance of being divided internally by transverse 
partitions. They are sometimes branched into two or three 
forks at the extremity, as in Alyssum, some species of Apar- 
gia, &c. Occasionally they emit little branches along their 
whole length : when such branches are very short, the hairs 
are said to be toothed or toothletted, as in the fruit of Torilis 
Antliriscus; when they are something longer, the hairs are 
called branched, as in the petioles of the gooseberry ; if longer 
and finer still, the term is pinnate, as in Hieracium Pilosella ; 
if the branches are themselves pinnate, as in Hieracium undu- 
latum, the hairs are then said to be plumose. It sometimes 
happens that little branchlets are produced on one side only 
of a hair, as on the leaves of Siegesbeckia orientalis, in which 
case the hair is called one-sided (secundatus) ; very rarely they 
appear upon the articulations of the hair, which in that case is 
called ganglioneous. (Plate I. fig. 9. Verbascum Lychnitis) : 
the poils en goupillon of De Candolle are referable to this form. 
Besides these, there are many other modifications : hairs are 
conical, cylindrical, or moniliform, thickened slightly at the 
articulations (torulose), as in Lamium album, or much en- 
larged at the same point (nodulose), as in the calyx of Achy- 
ranthes lappacea. 
Hairs are sometimes said to be Jixed by their middle 
.(Plate I. fig. 10. c.)\ a remarkable structure, common to many 
different genera ; as Capsella, Malpighia, Indigofera, &c. 
This expression, however, like many others commonly used 
in botany, conveys a false idea of the real structure of such 
hairs. They are in reality formed by an elevation of one 
bladder of the cuticle above the level of the rest, and by the 
developement of a simple hair from its two opposite sides. 
Such would be more correctly named divaricating hairs. 
