78 Campbell. — On the Prothallium and Embryo of 
Owing to the extreme shortness of the stem, it is difficult to 
determine whether it possesses a fibro-vascular bundle distinct 
from that of the leaves : but before the second leaf is clearly 
evident, procambium-cells are formed which seem to belong 
properly to the stem, and to arise from the inner cells of the 
segments of the apical cell. 
The Root . — The root of the mature sporophyteof Osmunda x 
differs much from that of the true Leptosporangiatae, and it 
was an interesting question whether a study of the root of the 
embryo would throw any light upon the significance of these 
differences. In both species considered here, the later roots 
have usually a four-sided apical cell which shows less regularity 
in its divisions than is the case in ferns with the ordinary 
three-sided cell. (In O. regalis, according to Bower 1 2 , there 
may be either a single three- or four-sided cell, or a group of 
initials. Todea according to Douliot and Van Tieghem 3 has 
a three-sided apical cell.) The root originates from the 
lower hypobasal quadrant, as in other Filicineae. 
As with the leaf, the direction of growth varies a good deal, 
and is dependent upon the same causes. If the octant wall 
is oblique (which happens regularly in some ferns, e. g. 
Pilularia ), the larger of the resultant octants becomes at once 
the apical cell ; but if the two octants are of equal size, it is 
not possible to determine at first which is to be the apical cell. 
Most frequently the first segments are formed parallel with 
the quadrant wall and the axis of growth becomes very soon 
almost vertical, but it is sometimes for a short time horizontal. 
Owing to this variation, sections were usually somewhat oblique, 
and it was often difficult to see clearly either the form of the 
apical cell or its divisions. 
When, however, the sections passed straight through it, the 
appearance was the same, both in longitudinal and transverse 
section, and it appeared triangular. That is, in the embryo 
1 Campbell, Notes on the roots of Osmunda and Botrychium ; Bot. Gazette, 
March 1891. 
2 Bower, The Meristems of Ferns ; Annals of Botany, Vol. III. no. xi. pp. 310, 
31 1. 3 Bower, 1 . c. p. 388. 
