REJUVENESCENCE IN NATURE. 201 



Algae (e.g. Vaucheria, Spirogyra, Sp/ieeroplea, (Edogo- 

 nium, Bul&oc/itete, Cylindrospermum, Rivularia, Palmo- 

 glceaY In the spores of Characeae we find a small 

 quantity of an often dark -yellow oil among the numerous 

 starch-grains ; the large spores of Marsilea also contain 

 a dirty-yellow fixed oil, besides starch. That the collec- 

 tions of fixed oil, so frequent in tubers and seeds, are at 

 least partially used up as nutriment, i. e. become trans- 

 formed in such a manner that they may subserve the 

 vegetative processes over again, is a fact not admitting of 

 doubt, although not yet sufficiently explained in its chemical 

 relations. Certain experiences of the Algae referring here, 

 not only confirm this transformation of the fixed oil, but 

 also indicate that the necessity of a condition of rest for 

 most seeds, as well as for most tuberous and bulbous 

 plants, is connected, at least in part, with this trans- 

 formation of the fixed oils.* 



In Sjjiroffyra the green spiral bands undergo a remark- 

 able change in those cells destined for conjugation ; their 

 regular course becomes interrupted by curvatures of 

 different kinds ; the beautifully toothed margins vanish ; 

 among and beside the simple or compound starch-grains 

 previously present, lying in the median line of the 

 bands, numerous oil-drops are found, at first very 

 small, but some becoming as large as the starch-grains, 

 which are distinguished from the latter even by their 

 brilliancy, but still more certainly on the application of 

 iodine. Through the union of the contents of the con- 



* Schleiden (' Grundz.,' 2te Auft. ii, p. 432 ; ' Principles,' p. 462, in the 

 chapter on Germination) proposes the question, " Whence does it arise that 

 the conditions which can and must introduce a determinate process into the 

 embryo, are capable of remaining a long period without action ?" and he 

 connects with this the conjecture that the cause of this phenomenon may 

 depend upon unknown slow chemical processes. The observations which 

 follow indicate that one of these processes must be sought for in the 

 gradual transformation of the fixed oil througli contact with atmospheric air, 

 which contact is brought about or else increased by drying. The well- 

 known phenomenon that many oily seeds, for instance those of the Cucur- 

 bitaceae, germinate more certainly and readily after having been kept dried 

 for a number of years, than in the first year, is certainly explained by this. 



