OF VEGETABLE TISSUE. ]9 



bark of trees. These spots are in the first in- 

 stance oval lengthwise, then round, and after- 

 wards transversely elongated. They present a 

 remarkable and very smooth surface, as if the 

 cuticle were dried up : they often become swollen, 

 and end by splitting asunder. Below the cuticle 

 is a substance, sometimes green, sometimes white, 

 which appears to be composed of detached cells, 

 in the form of egg-shaped bladders. It is from 

 these organs that such roots are put forth, as 

 shoot from branches, whether spontaneously, or 

 when plunged in earth ; they may with truth be 

 called root buds. They differ from the ordinary 

 buds which produce leaves or flowers, both by 

 their form and position : they absorb nothing 

 from without, as the spongioles do, nor do they 

 appear at all to serve the purpose of evaporation, 

 like the stomata. 



10. Glands, in the animal economy, signify 

 those organs which have the power of elaborating 

 some peculiar fluid from the nutritive juices of 

 the body. The word preserves the same mean- 

 ing when applied to vegetable anatomy. 



11. Hairs (pili, villi). Vegetable hairs are 

 prolongations of one or many cells, which by 

 their length rise above the surface: they are 

 principally glandular and lymphatic ; the former 



