72 TEXTURE OF VEGETABLES. 



noticed. They are composed of an assemblage of 

 elongated cells which have collectively been compared 

 to a bundle of tangent reeds, and individually to a straw 

 of wheat whose cavity is occasionally interrupted by 

 the joints. " The membrane of which they are formed 

 is often pierced with a great number of pores ; but is 

 at the same time thick and strong, being cut with diffi- 

 culty in a transverse direction, though in a longitudinal 

 direction it is divisible without effort. M. Mirbel says 

 the solidity of the vegetable depends upon the number 

 of interrupted or cellular tubes. They are not discov 

 erable in the embryo, nor even in the young plant at a 

 very early period, but only when the parts have been 

 fully developed, in which stage they are discoverable 

 in most plants without much difficulty, pervading the 

 ramifications of the branched Lichens, and the stems of 

 the Mosses ; surrounding the fibrous tubes of herba- 

 ceous plants, and constituting also longitudinal fibre ; 

 and intermingling themselves even with the fibrous 

 tubes of woody plants, and constituting part of the lig- 

 neous layers, as well as the prominent ridges with which 

 the surface of vegetables is marked. In the finer and 

 more delicate parts of the plant they are also equally 

 prevalent, but here they assume a different aspect, 

 and acquire a degree of consistence resembling that of 

 the cellular tissue."* 



Thus it appears according to the observations of Mir- 

 bel and others that the structure of vegetables is en- 

 tirelv vascular being an assemblage of tubes and cells 

 which are formed by the foldings of a membrane so col- 

 ourless, transparent and fine that no one has been able 

 to discover any traces of its organization. The form 



* Keith. 



