STRUCTURE.] FORMS OF HAIRS. 153 



Silky (sericeus), when they are long, very fine, and pressed 

 closely to the surface, so as to present a sublucid silky 

 appearance : ex. Protea argentea. 



Arachnoid, when very long, and loosely entangled, so as to 

 resemble cobweb: ex. Calceolaria arachnoidea. 



Manicate, when interwoven into a mass that can be easily 

 separated from the surface : ex. Cacalia canescens, Bu- 

 pleurum giganteum. 



Bearded (barbatus), when the hairs are long, and placed in 

 tufts: ex. the lip of Chelone barbata. 



Rough (asper), when the surface is clothed with hairs, the 

 lower joint of which resembles a little bulb, and the 

 upper a short rigid bristle : ex. Borago officinalis. 



Stellate, or starry, when the hairs grow in tufts from the sur- 

 face, and diverge a little from their centre, as in the 

 Mallow tribe. 



Hairs are either formed of a single cell of cellular tissue 

 (Plate I. fig. 8. b, and Plate II. fig. 18.) 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 Apargia, &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 Anthriscus ; when they 

 are something longer, the hairs are called branched, as in the 

 petioles of the gooseberry; if longer and finer still, the hair 

 is pinnate, as in Hieracium Pilosella; if the branches are 

 themselves pinnate, as in Hieracium undulatum, 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 1. fig. 9. Verbascum Lychnitis) : the 

 polls en goupillon of De Candolle are referable to this form. 

 Besides these, there are many other modifications : hairs are 



