BETEROMORPHISM ami ALTERNATION OF GENERATIONS. Mi!) 



Fumkia and Allium, in both of which normal fertilization takes place. It is 

 interesting to note thai in the case of Allium odorv/m recent investigations show 



that tli'- accessory embryos arise actually from tin' (uitijioiial <<//* (<;/'. pp. 41ti, 

 1 1 7 i. i.e. from cells at the base of the emhryo-sac which, in ordinary cases, simply 

 atrophy. Usually one embryo only .irises from this source, but occasionally all 

 three antipodal cells develop into embryos. The ultimate Eate of the embryo 



arising (by fertilization) from the egg-cell anil of those arising from the antipodal 

 cells has not been ascertained. 



A peculiarity of parthenogenesis consists in the fact that the brood-bodies 

 arising in the ovules assume the form of embryos, not distinguishable from 

 embryos resulting from fertilization of an egg-cell. Little tubers or buds produced 

 in the ovary in places of ovules, as in Ama/rylMa and Crimim (cf. p. 44), partake of 

 the nature of branches of the plant producing them; but the offshoots which arise 

 within 1 1\ ales are not branches but young plants, provided with root, stem, and leaves, 

 and they are nourished by a special tissue which cauuot be interpreted as a portion 

 of the axis of the young plant. These offshoots arising within the ovule possess 

 a new and independent axis, and herein exhibit an essential difference from the 

 offshoots described in the last chapter. Why these offshoots in the ovules always 

 assume the guise of embryos is a problem which we shall not solve, perhaps, until 

 we have more knowledge as to the essential differences in property between the 

 protoplasm of the ovule and that of other plant-organs. 



HETEROMORPHISM AND ALTERNATION OF GENERATIONS. 



A sight of the sea-anemones and ever-varying polyps and corals, viewed through 

 the blue-green waters of a shallow bay, at first suggests a kaleidoscopic assemblage 

 of blossoming plants. At a distance the crowns of expanded tentacles resemble' 

 red and purple Asters or the flowers of Mesembryanthemums; the skeletons of 

 these organisms are not unlike, in their ramification, the branching of some tufted 

 plant. The corals and polyps, like plants, are denied free movement, and like red 

 and other seaweeds, are attached to their stony substratum. Very appropriate 

 then, in view of their characteristic appearance, is the name of Zoophytes which 

 Zoologists gave to these animals. 



And in their internal structure and mode of life they present certain remarkable 

 points of resemblance to plants. In many species the single individuals which are 

 joined together into a colony behave quite like the organs of a bodj T , or the mem- 

 bers of a single organism which discharge different functions. There is a division 

 of labour amongst the individuals or polyps of the colony. One branch of the 

 colony is concerned in the acquiring of nutrition, another in reproduction, yet they 

 have a common digestive cavity, so that the juices obtained by one portion may be 

 Bhared by others which cannot take them up from the environment for themselves. 

 To this differentiation amongst equivalent members we may apply the term Hetero- 



