REJUVENESCENCE IN NAtUllE. 197 



during the period of rest (the winter or summer sleep), 

 points to the destination of starch in the economy of 

 vegetable life. Thus we find starch deposited in especial 

 abundance in tuberously thickened roots {e. g.. Curcuma 

 leucorhiza), in the subterraneous stolons forming propa- 

 gation-tubers (potato), in perennial rhizomes {Iris, Arum, 

 Isoetes*), in subterranean buds and bulbs (Liliaceae), in 

 the seeds of the Phanerogamia, either in the albumen 

 (Graminacese, Polygoneae, Chenopodiaceae), or the em- 

 bryo (Leguminosse, Castanea, JEsculus), and also in the 

 spores of many Cryptogamia (e. ff., Characese and 

 Rhizocarpese). We find some starch deposited even in 

 the bark and alburnun of trees in the winter. At the 

 re-awakening of vegetation a new formative activity 

 sometimes presents itself in these same organs and the 

 same cells, as in the embryo and spores awakening from 

 the seed-sleep ; sometimes the tissue filled with starch is 

 merely subservient, preparing nourishment for other 

 organs in course of development, by the process of 

 solution taking place in it, dying away itself after ful- 

 filling this destination, as is the case in the albumen of 

 seeds, the tubers of the potato, the thick cotyledon of the 

 chesnut. But the occurrence of solution of starch is 

 not confined merely tosuch Rejuvenescence connected with 

 the changes- of the seasons : I have observed it oftentimes 

 in the Algae in the midst of summer, and without a 

 preceding period of rest, in progress of transition to 

 propagation, in particular in the preparatory stages of 

 the formation of goiiidia. Hydrodictyon exhibits the fol- 

 lowing phenomena in this respect. The grains of starchf 

 forming gradually in the course of the period of growth 

 of the net, raake their first appearance as minute globules 

 (or vesicles ?) from gggth to jgsth of a millim. diameter, of 



Algse, (ChrooooccacesB, Oscillatorinese, Nostochinese, &c.), both starch and 

 clilorophyU are deficient. (Nageli, ' Einz. Alg.,' p. 5.) 



* In the cake-shaped rhizome of Isoetes lacustris there is an abundant 

 quantity of starch, but only slight traces of oil, while in the rhizomes of the 

 terrestrial species there exists a preponderance of fixed oil ; (see p. 200.) 



t See above, pp. 172, 192. 



