ROOT. 9 



39. Hairs , in all their varieties from Down to Bristles, 

 are other appendages of the epidermis of plants, and 

 are formed of one or more cells of cellular tissue deve- 

 loped in an elongated form, and sometimes having, as 

 in the Nettle, a glandular apparatus at their base. 



40. Prickles are modifications of hairs in which con- 

 tinued deposition of layer upon layer of cellular tissue 

 has gone on, and the cells of the tissue become conti- 

 nuous with one another. 



41. Glands are cells of cellular tissue which are some- 

 times enlarged and sometimes not, and arranged in an 

 aggregate or simple manner as appendages of the epi- 

 dermis, but which are chiefly characterized by their pe- 

 culiar offices. Sometimes they are sessile upon the sur- 

 face of the epidermis, and at others have an elongated 

 cellular stalk. There is a particular kind of gland called 

 the Lenticular ; these glands are seen upon the external 

 surface of young twigs and branches, especially of the 

 Willow : they have been supposed by some to be root 

 buds which, when placed in water, gave origin to such 

 organs. This view has been controverted. The origin 

 of them appears to be from the external portion of the 

 bark, and they are destitute of any true communication 

 with the internal layers of it. 



SPECIAL DIVISIONS OF THE Axis. 

 Root. 



42. A root is characterized by the following circum- 

 stances : by having no development of appendages upon 

 its surface like leaves or scales ; by its epidermis being 

 destitute of stomata, and its divisions being irregular 

 and not proceeding from buds. In most roots no pith 

 exists ; they are mostly destitute of true spiral vessels, 

 and they do not exhibit the colour green : to these, 

 however, there are exceptions to be found. 



