200 STECKBECK— ON COMPARATIVE HISTOLOGY 



are invested by a cellulose mantle which is usually quite thick. When 

 the crystals are too small to touch the cell walls, the cellulose envelope 

 at the ends of the crystals is prolonged into cellulose beams which are in 

 contact with the cell membranes. 



Coester (9), in his study of Mimosas, states that calcium oxalate 

 crystals are deposited in all plant parts of these sensitives. Two forms 

 of crystals occur— as individual twin crystals and as crystal clusters. 

 The former kind is found in all the forms examined, occurring as mono- 

 cHnic plates, or styloid-like crystals. Coester further says that the 

 presence of the crystals is generally associated with the vascular bundles. 

 Here they are enclosed in the parenchyma cells around the bundles. 

 The formation of crystals is so abundant that over the larger veins of 

 the leaves every cell contains a crystal. When viewed from the surface, 

 the vascular bundle appears to be covered by crystals, arranged in 

 regular series. The crystal system is usually found in connection 

 with even the smallest bundles. Crystals are found in the stems as 

 well as in the leaves. 



Solereder (43, p. 266) refers to the wide distribution of crystals in 

 the Leguminosae, and says two types are present — crystal clusters, 

 which are very rare, and soHtary crystals, which have either the ordinary 

 rhombohedral shape, or that of small rods or styloids. "The ordinary 

 rhombohedra occur especially in the tissue accompanying the vascular 

 bundles of the veins, in the chambered fibers of the bast and wood, and 

 also in the primary cortex. Those crystals which are rod-shaped, or 

 resemble styloids are especially peculiar to the mesophyll, but occasion- 

 ally occur in the epidermis of the leaf, in the crystal-containing cham- 

 bered fibers of the bast and also accompanying the sclerenchyma of the 

 veins. They are, strictly speaking, not solitary, but hemitropic crystals, 

 consisting of two or more individual crystals, arranged with their longi- 

 tudinal axes in approximately the same direction." 



Solereder (43, p. 171) also refers to the crystals of the Oxalidaceae, 

 as occurring in the form of raphides, clustered crystals and solitary 

 crystals, but says nothing of the distribution of the crystals in the 

 different members of the family. 



Leguminosae 

 Piieraria Thunbergiana 

 This plant is native to the tropical and sub-tropical regions of Asia, 

 but grows very well in the temperate regions, where it has been intro- 



