176 UTRICULAR STRUCTURES. 



the smaller power of refracting light. The exact process 

 of the origin of the proliferous utricles is as yet unknown. 

 Perhaps minute portions of the homogeneous mucilage of 

 the cell become individualized, acquire a globular shape, 

 and produce a membrane on their surface. Propagation 

 has not yet been observed in the proliferous utricles. 



The proliferous utricles lie free in the contents of their 

 cell, and are always of globular shape. They increase in 

 size up to a certain point. 



The contents of the proliferous utricles at first consist 

 of homogeneous mucilage ; this frequently becomes gra- 

 nular. In it originate several globules of starch- or chlo- 

 rophyll-granules.* The membrane of the proliferous 

 utricles is subsequently dissolved, and the starch-globules 

 and chlorophyll granules lie free in the cavity of the cell. 



6. Colour-utricles (Farbblaschen). 



These include the chlorophyll-granules, and the other 

 coloured globules of the cell-sap. They have already 

 here and there been called utricles, but no membrane has 

 been shown to exist upon them. Formerly, the starch- 

 globule, mostly present in their interior, was frequently 

 taken for a cavity. 



The following facts prove that the said structures are 

 actually utricles: a whitish membrane, surrounding the 

 green contents, may be clearly seen in the larger chloro- 

 phyll-utricles of the Algae, of the leaves of Mosses, of the 

 pro-embryo of Ferns (pi. II, fig. 10 a, b, c), of Characese 

 (fig. 17), and, in favorable cases, in the leaves of Phane- 

 rogamia (fig. 12 a /). When they lie close together, 

 they do not become blended into a mass, but, like cells, 

 acquire a parenchymatous form (fig. 11). By abnormal 

 alteration (in the pro-embryo of Ferns (fig. 10 d, ,/), 

 in the leaves of Mosses and Hepaticse), they become 



* On Caulerpa prolifera, by C. Nageli ; Zeitsclirift. f. wiss. Bot., Heft i, 

 1844, pi. iii, fig. 19. 



