io Protoplasm: 



2. Asexual. In the Asexual or Vegetative mode of giving rise 

 to new individuals, a single cell by ordinary vegetative division 

 produces one or more plants which in every respect are absolutely 

 the same as the plant which gave them origin. I may illustrate 

 the matter by pointing to the strawberry plant and the creeping 

 buttercup, both of which send off 'runners' or aerial branches from 

 the base of their stems, that at certain nodes send down roots into 

 the soil and rosettes of leaves upwards. In the course of a short 

 time the runners perish and then a number of independent indi- 

 viduals surround their parent. In potato plants, a 'stolon' or 

 underground branch stem bears at its end a swollen portion or 

 tuber which in the following year will produce a new plant in all 

 respects the same as that which bore the tuber. In these and 

 many other instances asexual is totally different from and inferior 

 to sexual reproduction. When, for instance, potato tubers are 

 planted in spring, the individuals that grow up from them are, as 

 1 have just said, identical with the plants from which the tubers 

 were taken. On the other hand, if ripe potato seeds are sown, 

 the young plants may reproduce any or all of the varieties of the 

 potato that had been known, and may sometimes produce new 

 varieties which are in men's appreciation better or worse than the 

 old. Thus by asexual reproduction the individual only is repro- 

 duced, and by the sexual mode the species. 



3. Parthenogenesis. The Parthenogenetic form of reproduction 

 occurs in a considerable number of the species of lower animals, 

 but not, so far as I know, in any of the higher. It takes place in 

 bees, wasps, silk-worm moths, sea-urchins, and in many species 

 of other families. In plants it is known among the Cryptogamia, 

 in a species of Stonewort, and in several species of mosses. A few 

 cases also are known among Flowering plants, as in one of the 

 Cudweeds, and in the annual Dog's Mercury, In these cases the 

 female ovum, without fusion with the complementary male body, 

 proceeds to divide and develop into a new individual. What is its 

 cause and its nature are not yet by any means understood, and 

 many experiments have been made to throw light upon the matter. 

 Unfertilized ova of several sea-urchins have been variously treated. 

 In some of the experiments the ova were shaken to detach and 

 eject the nucleus ; in others enucleated portions of the ova wer* 



