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 irt 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 sphero-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 



