THE EMBRYO 51 



sporophyte. In short, the strand of vascular tissue in the young sporophyte at the 

 time the first root emerges is composed solely of the coalescent strands of the root 

 and leaf exactly as is the case in the young sporophyte oiOphioglossum moluccanum, 

 and there is absolutely no trace of a cauline stele. 



The foot is composed of large parenchyma cells, which become smaller 

 toward the periphery, where they usually show more or less dense contents and some- 

 times fortn a quite definite layer of epithelium-like cells, which stain much more deeply 

 than the inner tissue of the foot. This outer layer of cells is presumably active in 

 the absorption of nutriment from the adjacent prothaUial tissue. Bruchmann states 

 that previous to the emergence of the root of the young sporophyte of 5. lunaria 

 the cells of the embryo are densely packed with granular matter of apparently 

 albuminous nature; but after the emergence of the root starch is developed abun- 

 dantly in the cells of the foot. This appears to be true also of 5. virginianum. 



Compared with B. virginianum, the embryo of 5. lunaria (fig. 36) is character- 

 ized by the lesser development of the foot and the later appearance and rudimentary 

 character of the stem apex and the cotyledon. 



The stem apex in B. lunaria (Bruchmann 2) is first evident as a slight superfi- 

 cial depression near the base of the massive root. A single superficial cell becomes 

 differentiated as the apical cell of the shoot, and a small group of cells is formed 

 before the rudimentary cotyledon develops. Both stem apex and cotyledon remain 

 very inconspicuous. The cotyledon is developed as a scale-like rudiment, which 

 never develops into a foliage leaf. Bruchmann states (Bruchmann 2, page 223) 

 that from seven to nine of these rudimentary leaves are developed before the first 

 green leaf appears above the earth. Hofmeister (Hofmeister 1) believed that three 

 of these rudimentary leaves were developed during the first year, and that the 

 second year the first spore-bearing leaf appeared above ground. Bruchmann thinks 

 that this is not the case and that the first spore-bearing leaf requires five years for its 

 development, as it does in the older sporophytes, and that only one leaf is formed 

 each year, as in the older plant. 



The first organ to penetrate the calyptra is, as we have seen, the root, which in 

 B. virginianum is very large and quite overshadows the relatively inconspicuous 

 bud at its base (fig. 7, 5). At the time the root first emerges the vascular bundles 

 still have the form of procambium, and it is not until the young root has a length of 

 several millimeters (5 to 20 millimeters, according to Jeffrey) that the first tracheary 

 tissue is developed. The first tracheary tissue arises at the base of the root and the 

 development, as usual, proceeds toward the apex. The primary root in Botrychium 

 virginianum is usually diarch, but triarch roots are sometimes found, and Jeffrey 

 says that the size of the root has no relation to the number of protoxylems formed. 

 The first tracheids are short and reticulately marked, as they are in Ophioglossum. 

 The surface of the root is quite destitute of root hairs, as is the case in the adult 

 sporophyte. 



In B. lunaria the predominance of the root over the shoot is even more marked 

 than in B. virginianum, for there are several roots, sometimes four to five, developed 

 before the first foliage leaf is formed, and the bud remains extremely small and 

 inconspicuous. 



A longitudinal section of the cotyledon oi B. virginianum, just before it breaks 

 through the overlying calyptra, shows it to be strongly cuiTed away from the root 

 and overhanging the cleft within which lies the stem apex. If the section is exactly 

 a median one, there may be seen near the tip, but lying somewhat toward the lower 

 side, a marginal cell of triangular outline, which, from the arrangement of the cells 

 about it, is evidently the apical cell. The cotyledon, instead of being straight as it 



