CELL-CONTENTS AND FORMS OF CELLS. 153 



If sections are mounted in a small quantity of water and 

 the latter replaced with dilute glycerin, followed by concentrated 

 glycerin, then there separates in the cells a number of yellowish 

 globules which are highly refractive (Fig. 93) ; these globules 

 tend to unite in the center and very soon crystallize. The sphero- 



FIG. 93. Hesperidin. A, B, formation of sphero-crystals in the epidermal cells of the 

 foliage leaves of Linden upon the addition of glycerin; in A the hesperidin occurs in highly 

 refracting globules, which in B have united in a large central globule in which a crystal- 

 aggregate has formed. C, crystals in stamen hair of the flower-bud of Verbascum. D, 

 crystals in the cells of the upper epidermis of Hyssopus officinalis. E, cells of the upper 

 epidermis of the foliage leaves of the Linden. -After Tunmann. 



crystal consists of radiating needles, the aggregate frequently 

 being marked by concentric lamellae, the whole being surrounded 

 by a more or less mucilaginous wall (Fig. 93). As there are 

 other substances in the cell the sphere-aggregate may contain 

 some of these in the interstices. If the crystals are formed slowly 

 and in the cold they are apt to be of a yellowish, or even dark 

 yellow, color, whereas if heat is employed and the crystallization 



