PROTECTIVE ARRANGEMENTS ON THE EPIDERMIS. 



323 



Koniga spinosa, a member of the Mediterranean flora. All these clothing hairs, 

 with star-shaped indented upper cells, are grouped together under the name of 

 " stellate hairs " (pili stellati). In Cruciferse and Malvaceae they occur in endless 

 variety. 



When the uppermost cell of the group forming the stellate hair is divided by 

 separation walls, which in part are placed perpendicularly to the leaf-surface, 

 branched hairs are the result. In branched hairs the branches, which are almost 



Fig /9 — Flinty armour of if oc/tea/aica(a 



1 Section perpendicular to the leaf-surface. 2 Surface view ; on the right hand the vesicular distended portion of a few 

 superficial cells is removed and the stomata are brought into view ; x350, 



always arranged in a stellate manner and are usually unicellular, can be dis- 

 tinguished from the part which supports the branches. This portion usually looks 

 like a pedestal, and is sometimes multicellular, sometimes formed from a single cell. 

 When the pedestal is very short, and the cell supported by it is divided by several 

 radiating divergent septa, which are either oblique or perpendicular to the leaf- 

 surface, tufted hairs {'pili fasciculati) are formed. These look like sea-urchins 

 lying on the surface in close proximity to each other; they vary very much in the 

 size, number, length, and direction of their branches, and they are particularly 

 abundant on the cinquefoils (Potentilla cinerea and arenaria), cistus and rock- 

 roses (Cistus and Helianthemwm). A common form is represented in fig. 78^. 

 When the foot-stalk is very short, and the radiating branch -cells borne by it are 



