REJUVENESCENCE IN NATURE. 195 



less all parts of these; we see it most clearly in the 

 behaviour of starch or of amylon, of the fixed oils, as also 

 of the nucleus. There are certain products of cell-life 

 which furnish a measure of the age of the cell. While 

 the formation of chlorophyll is especially proper to the 

 more vigorous youth of the cell, we see in the formation 

 of starch and oil, in the interior of the cell, just as in the 

 formation of cellulose-layers upon its surface, the com- 

 mencement of a limitation and quieting of the vital 

 activity, which marks the more advanced age, with the 

 distinction, however, that the preponderating formation 

 of cell-membrane (the process of lignification) usually 

 results in the permanent death of the cell, while the 

 filling of the cell with starch or oil brings with it a 

 condition of sleep, from which it may awake, under 

 certain circumstances, even after thousands of years, as is 

 proved by the well-known experiments on the germination 

 of grains of wheat from the tombs of the Egyptian 

 kings. This is more particularly true of the condition of 

 rest produced by formation of starch, while the formation 

 of oil, although frequently, is not always accompanied by 

 a condition of the cell in which it is capable of Rejuve- 

 nescence. 



The formation of chlorophyll stands in inverse pro- 

 portion to that of starch and the fixed oils, in the cells ; 

 while starch and oil appear in greatest abundance in the 

 old age of the cell, and are again either wholly or partially 

 destroyed in its Rejuvenescence, the green colouring 

 matter, on the direct reverse, vanishes in the old age of 

 the cells, reappearing in their Rejuvenescence. Thus the 

 leaves of the ivy are coloured more or less with brownish 

 red in winter, and grow green again in spring. The 

 embryos of many seeds are green in the earliest period of 

 formation, but as the seed ripens, passing into the stage 

 of sleep, they become white, from the chlorophyll dis- 

 appearing and the cell becoming filled with starch or oil, 

 till finally, in germination, awakening to new life, they 

 again acquire a green colour. The contents of the spores 



