358 BOTANICAL GAZETTE [may 
sists of compact angular fragments 1 cm. or more square, very 
white and pure, derived evidently from a layer precipitated in 
water. Professor SENN of Basel has kindly examined the specimen 
and I owe to him the accompanying drawings and the following 
description: 
“The starch in question consists for the most part of combined 
grains. The grains joined in pairs have one side parabolically 
Fic. 2.—Starch of Pleridium aquilinum: explanation in text 
rounded, while the side in contact is plane (fig. 2, a-c). Where 
there are several parts combined, they are placed sometimes one 
behind the other, sometimes one beside the other (fig. 2, /). The 
diameter of the grains vary from 3 to 18 #; the average diameter 
is between 6.5 and 3 4. The structure is slightly eccentric, 
depending on the arrangement by layers, which are not very evi- 
dent except by examination with polarized light. The dark cross 
obtained by crossed Nicols is near the rounded end, and is seen 
especially in grains somewhat elongated (fig. 2, d and f). By @ 
greater enlargement the nucleus of the layers can be observed 
(fig. 2,a). In the nearly globular grains the two dark striae cross 
in the middle (fig. 2, ¢). When the grains are submerged in water 
and under pressure of the cover glass, irregular cracks are seen, 
