46o 
EDWARD F. WOODCOCK 
If attention is now turned to a consideration of Polygonum aviculare 
and Polygonum tenue, it is seen that the development of these two 
species appears practically identical, therefore, the variations from the 
type will be followed only in Polygonum aviculare. The early stages 
are essentially the same, figure I representing very well the condition 
at the octant stage for both species. The nucellus of P. aviculare, 
however, becomes degenerated to a slightly greater extent. As growth 
proceeds beyond this point, the method of development is the same 
but the rapidity of endosperm formation is much greater. Ac the 
time of the first indications of cotyledons in the embryo, the embryo 
sac is already filled with cellular endosperm, and the nucellus has been 
reduced to a few crushed cells at the base of the seed, and the nutritive 
layer. The haustorium-like mass of protoplasm at the base of the 
seed is much broader. The suspensor of the embryo is made up of 
four cells, instead of only two as in the majority of seeds of P. Persi- 
caria. 
The later development follows much the same plan, the growing 
embryo coming to lie in one of the corners of the seed. At maturity 
{figs. 5 and 8), the seed is 2.35 mm. long and 1.26 mm. wide. The 
embryo is longer than in P. Persicaria, and extends across the chalazal 
region. The cotyledons are semicircular in outline (fig. 8, C) and the 
cotyledon away from the starchy endosperm lies with its back against 
the chalazal region of the seed. As growth has proceeded, the coty- 
ledon next the endosperm has grown down over the other cotyledon. 
The cylindrical, massive hypocotyl is the same width as the cotyledons 
at the base of which appears a well-developed, cylindrical plumule 
(fig- 5, p)- 
Polygonum Convolvulus and Polygonum sagittatum agree in most 
respects with the type. At the octant stage of P. Convolvulus {fig. 6), 
however, the ovule is much broader and the integuments relatively 
thicker than in P. Persicaria. At maturity, the cotyledons are rather 
broad and flattened, the edges pressing against the base of the seed 
wich the tips well past the middle line of the seed. The position of the 
cotyledons with respect to the chalazal region of the seed agrees with 
the condition found in P. Persicaria, but differs from that found in 
P. aviculare and P. tenue, in which the back of the outer cotyledon lies 
pressed against the chalazal region of the seed. Figures 7 and 10 
represent the mature condition found in P. Convolvulus, and may 
also serve the same purpose for P. sagittatum, except that in the latter 
species the cotyledons are somewhat broader. 
