130 
IOWA ACADEMY OF SCIENCES. 
this family have been studied, but in some cases not all the 
species. The representatives of the different sub- genera have 
been studied except in Bistorta which was omitted for want of 
good material. The palisade portion constitutes the outer 
part of the achenium; this is followed, in most cases, by the 
testa, consisting of several layers of cells, varying in some 
cases however; they are quite regular in form and in some cases 
are dark in color. In a mature palisade cell the cell- cavity is 
present. This varies greatly in the different genera, in some 
cases occupying nearly the entire cell; in others it is small and 
irregular. The light line does not occur and hence they differ 
materially from the malpighian cells found in Malvacece, Legumi- 
nosce, etc. Elongated cells of this character, without the light 
line have been called palisade, but this term is preoccupied by 
one used for the elongated cells found in the leaf, i. e. the 
so-called palisade parenchyma. I shall therefore use the term 
“palisade” in quotation marks. For brevity I shall refer to 
section of fruit and seed coat as achenmium. 
Polygonum virginianum, L. 
Figure 1, plate vii. 
In the specimens of this species the “palisade” cells are 
long and narrow, with a cell cavity extending the whole length 
of the ceil. The cell is nearly truncate at the ends, but sends 
out from its sides minute canals. The whole cell is colored 
light brown, while the cavities are of a deeper color. The ‘ ‘ sub- 
palisade” portion consists of four layers of nearly square 
cells arranged systematically. The endosperm is composed of 
large, irregular cells, containing both simple and compound 
starch grains. Measurements — achenium 165u, “sub-palisade”" 
cells, 132u, “sub-palisade” 33u. 
P. convolvulus, L. 
Figure 2. plate viii. 
In this species the “palisade” cells are long but not as narrow 
as in P. Virginianum, while the cell cavity is also broader, the 
cavity has some canals as in that species, but in addition to this 
occur papillate projections. The whole cell is clear and light, 
while the cell-cavity is light brown. The ' ‘sub-palisade” portion 
consists of four layers of isodiametric cells. The endosperm 
is made up of long, regular cells of about the same size as 
P. Virginianum. Measurements — achenium, 132u, “palisade”" 
cells, 99u, “sub-palisade,” 33u. 
