DEVELOPMENT OF SEED IN POLYGONACEAE 
455 
even though there is an absence of perisperm in Fagopyrum esculentum, 
the other members of the Polygonaceae may perhaps be characterized 
by perisperm at maturity. In the order Scitaminales Humphrey 
found that the Musaceae are characterized by an abundant starch- 
bearing endosperm, the Zingiberaceae and Cannaceae by a thin layer 
of aleurone or proteid-containing endosperm, and the Marantaceae by 
an apparent absence of endosperm in the mature seed. Humphrey 
also pointed out a variation even in a single family. Among the 
Musaceae, Heliconia shows a narrow layer of functional perisperm 
around the endosperm; while in Strelitzia, the perisperm becomes 
reduced to a thin layer of broken down tissue. 
Among the earlier writers who have dealt with the Polygonaceae, 
Strasburger (20), in 1879, described in detail the development of the 
mature embryo sac in Polygonum divaricatum, taking up the arrange- 
ment of the cells in the flower rudiments, the plan of the ovule and 
embryo sac and the development of the latter. He includes a brief 
description of the formation of the integuments and the course of the 
vascular bundle in the ovary and ovule, but says nothing regarding the 
morphology of the seed in its later development. In a later work 
(1902), Strasburger also simply describes Polygonum orientale with 
respect to the arrangement of the parts at the time of the mature 
embryo sac. 
Dammer, writing on the Polygonaceae in Engler and Prantl (6), 
described the fruit and seed of Polygonaceae, dealing with the adapta- 
tions for dissemination, rather than the morphology of the seed. 
The writer has made a careful study of certain genera of the 
Polygonaceae to determine if the absence of perisperm as a storage 
tissue noted in Fagopyrum by Stevens (19 12), holds in the mature 
seed of other Polygonaceae. The genera under observation have been 
Polygonum, Polygonella, Rumex, and Rheum. In each of these genera, 
one or more representative species have been taken into consideration. 
The material on which this study was made was collected during 
the summer of 191 1 and 1912, and killed in weak chromo-acetic acid. 
Sections were cut about 12 ju in thickness and stained with Delafield's 
haematoxylon. An interpretation of the exact position and shape 
of the embryo in the mature seed was gained by free hand dissections 
under the binocular microscope. 
A further study of the changes which occur in the seed tissues of 
Fagopyrum, Polygonella, Polygonum, and Rumex during the process 
of germination has also been carried on by the writer. 
