SECT. I. OBGANOGBAPHY AND GLOSSOLOGY. 19 



bonaceous material, which ultimately fills them, and 

 gives consistency to the stem. The juicy contents of 

 some cells are highly coloured ; and even contiguous 

 cells often contain liquids of different tints, although 

 there is no apparent difference in their structure, 

 which might indicate some cause for such diversity. 

 Indeed, the brilliant hues of flowers, and the various 

 tints of the foliage, all depend upon the coloured juices, 

 or the globules floating in them, which are contained in 

 the vesicles of the cellular tissue, and have been elabo- 

 rated by them ; but they never depend upon the or- 

 ganic membrane itself, of which they are composed, 

 and which is always colourless, or, at best, only slightly 

 tinged with green. 



(20.) Raphides. But, besides the strictly organic 

 compounds, there are also certain chemical combinations 

 whose results appear in the form of minute crystalline 

 spiculce, which have been deposited from the heteroge- 

 neous admixture contained in the cells. These have 

 been termed " raphides," and were originally considered 

 to be organised bodies. One of most common occur- 

 rence, is the oxalate of lime, the crystals of which are 

 sometimes of such magnitude, and their forms so com- 

 plete, that the law of their crystallographic structure 

 may be readily recognised. 



(21.) Cavities in the Tissue. Besides the intercel- 

 lular passages mentioned above (art. 17-); there are 

 other well-defined cavities in the cellular tissue, which 

 serve either for the reception of various secreted matters, 

 as resins, oils, &c., or else contain air. The former are 

 termed " receptacles," or "vasa propria," and are com- 

 monly of a spheroidal, cylindrical, or oblong form, the 

 result of an enlargement of the intercellular passages, 

 or of a rupture in the tissue itself. The latter are 

 termed "air-cells," or "lacuna?;" and, although these 

 are most frequently very irregular in their form, they 

 are often constructed in a more definite manner than 

 the receptacles, and then consist of extremely regular 

 c 2 



