Fe ty ae A eee ee he 
sen = 
Ais 
wa Bake i ets oe i SS Ta ea 
1912] : STEV ENS—SEED OF BUCKWHEAT 63 
“tapetum” derived from the integument in numerous genera, 
notably Linum, Geranium, Primula, Phacelia, and Lobelia. 
Lioyp (10, p. 103) has recently shown that in the date the in- 
tegument serves to some extent to distribute nutritive material to 
the developing endosperm. In the buckwheat, however, the integu- 
Fics. 4-6.—Fig. 4, portion of longitudinal section at about the stage shown in 
fig. 3; only the cute ie of the nucellus, the “nutritive jacket,’ remains functional; 
the endosperm shows an outer layer of embryonic cells and a more central region of 
large vacuolate cells; some of the larger cells contain starch grains; X 260; fig. 5, later 
stage; the cells of the nutritive jacket have become vacuolate; X 260; 
grain; the nucellus remains merely as a thin region of crushed cells; the uber layer 
of endosperm cells is differentiated as an aleuron layer, the other endosperm cells are 
crowded with starch; 260; J, integuments; N, nucellus; EZ, endosperm; A, aleuron 
layer. 
ments seem to have no part in this process. In fact, they undergo 
very little differentiation, but remain throughout the growth of 
the seed as thin, rather uniform structures, each consisting of but 
two layers of cells. As there are no vessels present in the ovule 
which might accomplish this work, it seems entirely probable that 
the outer layer of the nucellus functions for the transfer of nutritive 
