90 LATICIFEROUS TISSUE SCHULTZ. [BOOK i. 



with regard to other tissue, large and thick-sided when 

 old, but so capillary and thin when young as hardly to be 

 visible. The sides are not parallel as in other vessels, but 

 often contracted and expanded at intervals, so that they may 

 be described as partially closed up by strictures here and 

 there : they are said to have a power of contraction, but there 

 are no valves or dissepiments in their interior. The larger 

 trunks Schultz calls vasa expansa, and the finer ramifications 

 vasa contracta, 



This kind of tissue has generally an undulatory direction. 

 (Plate II. fig. 19). In its interior there is a quantity of 

 granular matter, which sometimes fills it wholly, and some- 

 times is separated by empty spaces. Its average size is 

 1 4*0 of an inch. The sides, although they thicken by the 

 successive deposit of new matter, never offer any marks, or 

 pits, or other interruptions of continuity. 



It is obvious from these characters that cinenchym is 

 different from every other form of tissue. Its constant, 

 irregular branching and anastomosing would alone distin- 

 guish it. 



As such vessels lie in no definite direction with respect to 

 the rest of the tissue, they have been generally overlooked, 

 and are often very difficult to find, although always present in 

 the greater part of flowering plants. M. Schultz recommends 

 maceration for five or six days, as affording a ready means of 

 separating them from the surrounding tissue; and I quite 

 concur with him in this recommendation. It is, however, 

 easy to find them in the liber of the Fig, in the roots of 

 Dandelion, Scorzonera, Lettuce, and other milky Composites, 

 or in any of the parts of Chelidonium. 



They are placed in great abundance in the innermost 

 layers of the liber, across the Parenchym of foliaceous organs, 

 in the bark of the root, in the pith, and probably in all other 

 parts; but their station seems to vary in different species. 

 Sometimes they accompany the spiral vessels, forming a part 

 of the bundle of tissue to which those organs belong. From 

 the interior parts they proceed by finer and finer ramifi- 

 cations. 



In the lowest orders of plants, and in some others, they are 



