2So 



A TEXT-BOOK OF BOTANY. 



In the examination of technical products, as also in taxonomic 

 work, the study of plant hairs is very important. They show a 

 great diversity in form in not only genera and families but even 

 in related species. They vary considerably in their distribution 





Fig. 148. Mostly non-glandular hairs and a few of the small glandular hairs covering 

 the surface of the fruits of several species of Rhus: g, hairs on Rhus glabra, being more or 

 less broadly top-shaped or carrot-shape to spatulate and occasionally narrow elliptical and 

 from o.ioo to 0.400 mm. in length; b, hairs on Rhus typhina, being long and needle-like, 

 varying from 0.750 to 1.500 mm. in length; c, hairs of Rhus glabra borealis, being intermedi- 

 ate between those of Rhus glabra and Rhus typhina, varying from elongate spatulate and 

 narrow cylindrical to needle-shaped, and from o.ioo to i.ooo mm. in length. 



not only in related species, but sometimes in varieties of the same 

 species they show marked variation in size and form. In some 

 natural hybrids intermediate forms of hairs of the parent species 



