1911] CHRIST—FILICES WILSONIANAE 359 
which start often from the nucleus (fig. 2, b and c). The cause 
of these cracks is not the swelling but the pressure. In warm 
water the grains swell without cracks, and take the form of irregular 
linguiform corpuscles.” 
It is well known that the rhizomes of Pteridium have served 
on a large scale and still serve as food because of their richness in 
starch. - In New Zealand and Australia they have been much used, 
and the natives of the Canary Islands make use of them also 
(C. Botte, Standorte der Farne auf den Canarischen Inseln, 
Zeitschrift fiir Allg. Erdkunde, Neue Folge xiv. 304). In 1884 
I myself saw a peasant on the slope of Pic de Teneriffe dig up these 
rhizomes for this purpose. It is in the roasted and ground state 
that this root is used as food. According to Hooker (Spec. 
Fil. ii. 199), Dr. B. CLarKe has written an article (Hook. Jour. 
Bot. 9:212) recommending the use of this food. But the extrac- 
tion of starch as the Chinese of Ichang practice it seems to be 
very rare. I find, however, a citation of LABILLARDIERE which 
says: “Amylacea radicum substantia, quam eliciunt mandendo, 
silvicolae Cap. V. Diemen sustentantur” (AGARDH Recens. spec. 
gen. Pteridis 1839, p. 46). 
BASEL, SWITZERLAND 
