

UTRICULAR STRUCTURES. 177 



larger; the contents lose their colour, and pass into a 

 colourless fluid containing granules ; in this condition they 

 are undistinguishable from minute cells. The contents 

 of the chlorophyll-utricles undergo peculiar changes, which 

 chiefly consist in the origin of one or more starch-globules 

 (fig. 12). Green and red colour- vesicles manifest growth, 

 and in the course of this their shape is altered in various 

 ways. Finally, the chlorophyll-utricles divide like cells 

 (% 10 c). 



Since Mohl's researches* the chlorophyll- utricles have 

 commonly been regarded as a nucleus of one or more starch- 

 granules, on which chlorophyll has been deposited as a 

 coating. This view presupposes that the starch-granules 

 exist first, and that they are afterwards coated with chloro- 

 phyll. But the transition of starch-globules into chloro- 

 phyll-granules has nowhere been seen. On the other hand, 

 chlorophyll-utricles not unfrequently occur in the Algae 

 without a trace of starch in their interior. In some Algae, 

 moreover, as well as in higher plants, the origin and growth 

 of the starch-globules may be traced, in the interior of the 

 chlorophyll-utricles, up to the absorption of these latter. 



The colour-utricles are best named according to their 

 colour ; green, red, blue, or yellow colour-utricles, or even 

 with one word ; green utricles (chlorophyll-utricles), red 

 utricles, &c. 



I know nothing of the origin of colour-utricles free in 

 the cell-contents. They appear as minute (green or red) 

 granules, which, after they have reached a sufficient size, 

 display an utricular structure (fig. 10, a, b; fig. 12; fig. 17). 

 They originate by the division of a parent-utricle. This 

 becomes elongated, divides by a wall, and separates into 

 two new colour-utricles (fig. lOc). 



I have seen the division of the green colour-utricles in 

 Algae (e. g. in Bryopsis Balbisiana, Valonia ovalis], in 

 the pro-embryo of Ferns, and in Nitella. This division 

 sometimes presents such an appearance that we only see 



* Untersuchung. iib. die Anatom. Verhaltnisse des Chlorophylls. (Dis- 

 sertation, 1837, Verm. Schrift. p. 349.) 



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