1918] JONES—HETEROSIS 329 
as the egg cell are fertilized by nuclei of the same properties, and this takes 
place in double fertilization. Double fertilization occurs even when the reserve 
substances entirely or to a great extent are put directly into the embryo, 
we see that this is truly the case in many plants. In these plants nevis 
an endosperm at first develops and even results from double fertilization as 
1G. 3.—Crossed and selfed seeds from same inflorescence; top and side view of 
same seeds; crossed seeds above, selfed seeds below. 
well, so it is possible that such plants exhibit a retention of a character and that 
in them the fertilization of the endosperms is only a useless relic. So from our 
standpoint double fertilization can be taken as an apparent adaptation in two 
ways: first, to stimulate endosperm development; second, to alter the endo- 
sperm physiologically to accord as far as is possible with the embryo. In this 
way a good nourishment of the seedlings by the endosperm material is assured 
(loc. cit. pp. 502, 503). 
