98 



BOTANY. 



(6) One-celled simple hairs may be obtained from the vegetative 

 organs of species of CEiiothera and Brasgica and many (jrasses — e.g., 

 species of Panicum — and from the seeds of the cotton plant ; the last 

 constitute the " cotton" of commerce. 



(c) Many-celled simple hairs occur on the filaments of Tradescantia, 

 on leaves of the Primrose, Ageratum, Erigeron Ganadenae, pumpkin, 

 and very many others. 



(d) Branched one-celled hairs occur in OapseUa, Drdba, Sisymiryum, 

 Alyssum,, and many other Cruciferm. 



(e) Branched many-celled hairs may be found on the Mullein and 

 Ivy. 



6r^^ 



Kg. 88.— Hairs from Thistle (Cnieus altissimvs). ./i,yonng haii from the stem 

 Defore it has heen drawn out ; B, an older hair more highly magnified, after its ex- 

 tremity has heen drawn ont into a thread-like lash ; C, hair with a long lash from 

 the underside of a f nil-grown leaf. Highly magnified.— After Beal. 



(/) Clustered or tufted hairs are found on many MaZvacece, and the 

 nearly related scales or peltate hairs on Shepherdia. 



(g) Root-hairs are best obtained for study by growing seeds of mustard, 

 radish, wheat, etc., on damp cotton or blotting-paper, and then mak- 

 ing careful longitudinal sections of the terminal portion of the root at 

 the place vphere the hairs are just appearing (usually several millimetres 

 above the tip of the root). By making preparations in this way all 

 stages of the development of these haira may be studied in the same 

 specimen. 



(h) Glandular hairs are found in many groups of plants ; they may 

 be studied in Petunia, Verbena, Primvla, Martynia, and the tomato. 



(t) Apparently related to glandular hairs are the curious hairs from 



