64 BOTANICAL GAZETTE 
[JANUARY 
substances from the chalazal region to the growing endosperm. 
Such an explanation might account for the fact that the endosperm 
develops fastest in the upper portion, the broken down cells of the 
nucellus forming, lower down, an 
effective barrier to the passage 
of food material. 
In its later development the 
embryo becomes remarkably un- 
symmetrical, and as the cotyle- 
dons increase in size they become 
considerably curved. At matur- 
ity the cotyledons are broad and 
rather thin; and since the blade 
on one side of the midrib is twice 
as wide as on the other and the 
midribs lie together, one cotyle- 
don on each side extends con- 
siderably beyond the other. In 
a cross section of the seed they 
present the appearance of a much 
exaggerated letter S (fig. 8, C). 
This peculiarly unsymmetrical 
nature of the embryo makes the 
endosperm exceedingly irregular. 
Shortly before the seed is ma- 
ture, a further differentiation 
takes place in the endosperm. 
The cambium layer, after it has 
ceased cutting off starch storing 
cells, divides further by anticlinal 
walls; thus forming a continuous 
layer of short regular cells, filled 
in the mature seed with dense 
granular contents, but contain- 
ingno starch. This is an aleuron 
layer, the ‘“‘eiweisshaltige Zellen”’ 
Fics. 7, 8.—Fig. 7, longitudinal median 
section of mature seed; X15; fig. 8, trams 
verse section of mature seed, below the 
hypocotyl; 15; the parts of the embryo 
are shaded; E, endosperm; C, cotyledons: 
H, hypocotyl 
of Harz (fig. 6,A). Except for 
this single aleuron layer, the irregular endosperm consists of large, 
