230 



enon, and without the occurrence of any in.iury to stimulate growth. They 

 form in pitted trache;ii usually, though in some one-year old stems they 

 form in fibrously thickened tracheae without any perforations. 



The walls of the tyloses are delicate at tirst. but they afterwards 

 thicken somewhat, and their cellulose walls become lignitied like the rest 

 of the wood parenchyma. 



In Leopard-wood the tyloses have their walls so strongly thickened 

 that the cells resemble the stone cells in pears. Nearly all the tracheae 

 are tilled with them, rarely is there found a poi-tion of a trachea without 



Leopard-wood. Tang. Sect. ( x i 



them. The stone cells are irregular in shape, and are packed closely 

 together, usually one being sufficient to till the lumen transversely, though 

 sometimes two and three are wedged together across the lumen. The 

 walls vary considerably in thickness, some having their lumina entirely 

 obliterated, while in close proximity to them may be others with fairly 

 large lumina. Li all of them the thickening of the walls is in well-deflned 

 layers, the layers sonaetimes separating from each other. All the walls 

 are provided with fine canals, radiating from the central lumen, some- 

 times branched, and in all, the canals of adjoining cells corresponding. 



