450 Campbell . — The Gametophyte and Embryo of 
the very much older one shown in Text-fig. 7, in which the root had 
emerged from the gametophyte and the stem-apex and cotyledon were 
already well developed. It is, however, clear that the differentiation of the 
primary root and stem-apex occur much earlier in B. simplex than in 
B. lunaria, and in this respect B. simplex is more like B. virginianum or 
B. obliquum than it is like B. lunaria. 
Bruchmann’s Fig. 43 represents a stage intermediate between our 
Text-fig. 6 and the much older one shown in Text-fig. 7. This embryo of 
B. lunaria has the apical cell of the root clearly defined, and the stem-apex 
is recognizable, occupying a narrow cleft between the base of the extremely 
A 
Text-fig. 7. a. Nearly median section of a young sporophyte, in which the root has just 
emerged; the root, r, is cut obliquely; cot , the cotyledon; x, apex of the stem; / 2 , second leaf, 
x 45. b. Apex of the stem ; x } the apical cell, x 300. c. Apex of second leaf, x 300. Sections 
made by Dr. L. Baas-Becking. 
rudimentary cotyledon and the base of the massive root. At this stage the 
embryo consists almost entirely of the root and foot. 
B. simplex differs notably from B. lunaria in the earlier appearance of 
the stem-apex and cotyledon, and the much better development of the 
latter. The fully developed cotyledon was not seen by the writer, but 
Dr. L. Baas-Becking, who has been engaged in a study of the more 
advanced stages of the young sporophyte, has informed him that the 
cotyledon, though much less conspicuous than that of either B. obliquum or 
B. virginianum , develops a small lamina and is apparently functional. 
Text-fig. 7 shows a young sporophyte slightly older than that repre- 
sented by Bruchmann’s Fig. 45. The general relation of the parts is much 
the same, but the foot is less prominent in B. simplex , and the cotyledon and 
