8 BTTJ.F.Tiy 844, TJ. S. DEPARTMENT OF AGBICULTDRE. 
mature pollen grains is vacuolate, and it contains a fatty oil in the 
form of an emulsion. Soon after the pollen grains are formed, the 
walls of the mother cells disappear, thus permitting the pollen grains 
to he loose in the anther. 
FERTILIZATION IN MELTLOTUS ALBA. 
The time intervening between pollination and fertilization was 
investigated with both self-pollinated and cross-pollinated flowers. 
In cross-pollination the parents were separate plants. This point 
was investigated with plants out of doors during the summer of 1916 
and with plants in the greenhouse during the following winter. The 
time elapsing between pollination and fertilization ranged from 50 to 
55 hours and was not longer in the case of self-pollinated than with 
cross-pollinated flowers. Furthermore, the rate of the development 
of the embryo in each kind of pollination was studied and was found 
to be as rapid in self-pollination as in cross-pollination. Therefore, 
self-pollination is apparently as effective as cross-pollination in 
Mdilotus alba so far as the vigor of pollen tubes and the rate at which 
embryos develop are concerned. Ifelilotus officinalis was not studied 
in reference to this point. 
Considerable difference often exists in the size of the young embryos 
in the ovules of the same pod. This is due in part to a difference 
in the time of fertilization, although some of it is due to a difference 
in nourishment. It was observed that the ovule first fertilized 
might be an upper one. lower one. or any one between these. Occa- 
sionally one or more ovules are not fertilized. 
DEVELOPMENT OF THE SEED. 
A proembryo with a rather long suspensor is developed from the 
fertilized egg. (PI- H, fig. 2. The endosperm, which quite early 
forms a peripheral layer around the entire embryo sac, develops most 
rapidly about the embryo, which soon becomes thoroughly embedded 
in it. i,Pl. Ill, figs. 1 and 2. ; After the embryo has used up the 
endosperm in the micropylar end and has enlarged so much as to 
occupv nearly all bi the space in this region, the development of the 
endosperm becomes more active in the chalazal end, and when the 
embryo is mature there is very little endosperm left. 
The seed coat begins to form about the time of fertilization, 
although it apparently does not depend upon it, for in ovules where 
fertilization is prevented the outer integument undergoes the early 
modifications in the development of the seed coat before the ovule 
breaks down. The development of the seed coat is apparent first at 
the micropylar and chalazal ends, where the outer cells of the outer 
integument Become" much elongated and their outer walls thicken 
very soon after fertilization. The modifications in the development 
