316 



MANUAL OF BOTANY 



cl, cl). This kind of parencliyma is called coUenclii/ma ; it never 

 becomes lignified. Another variety of parenchyma is termed 

 sclerenchyma : this consists of cells which have become much 

 hardened by thickening layers and lignified, as in the stems of 

 Palms. CoUenchyma and sclerenchyma are also forms of 

 prosenchyma. 



In some of the lower orders of plants there is a peculiar kind 

 of tissue present, to which the names of Tela contexta and 

 interlacing fibrilliform tissue have been given. It occurs 

 chiefly in the Fungi {fig. 623), and consists of very long thread- 

 like cells, or strings of cells, simple or branched, with either 



Fig. 67(i. Fig. 677. Fig. 678 Fig. &T?. Fig. 680. Fig. 681. 



Fig. 676. Prosenclijmatous wood cells. Fig. 677. Transverse section of 



prosenchymatous cells, showing the thickness of their walls, m. Midflle 



lamella. Fig. 678. Prosenchymatous cells in combination. Fig. 679. 



Upper end of a bast fibre. Fig. 680. Branched fibre. After Schieiden. 



Fig. 681. Transverse section of fibres, showing the thickness of their walls. 



thin, soft, readily destructible walls, or dry and firm ones, the 

 whole inextricably interwoven or entangled with each other so 

 as to form a loose fibrilliform tissue. This tissue, which is 

 " usually known under the name of hyphce or hypJial tissue^ con- 

 stitutes, as a general rule, the vegetative portion of all Fungi. 

 In the larger Fungi this same tissue also forms a more compact 

 structure at certain parts, as on their surface, where it is arranged 

 as a kind of skin, and in the stalks, which are fii'equently of 

 some thickness. It then constitutes what is termed pseudo- 

 parenchyma. 



The varieties of parenchyma as just described constitute the 



