456 MOSSES AND FERNS chap. 



ous, but later enlarges more. Its cells are in close contact with 

 the prothallial cells. The root now grows rapidly downward, 

 penetrating through the prothallium until it reaches the ground. 

 The stem apex rapidly elongates and grows upward through the 

 calyptra. The embryo thus perforates the prothallium both 

 above and below, as in Marattia, although owing to the position 

 of the archegonium in the former, the relation of the embryo to 

 the archegonium is not the same. 



The root in E. hieinalc and E. arvcnse (Jeffrey (2), p. 169) 

 penetrates the earth before the shoot breaks through the calv])- 

 tra, but in E. liinosum, the emergence of the root occurs at a 

 much later period. At the time the shoot emerges from the 

 calyptra, there is already developed the rudiment of the bud 

 that is to form the second shoot. This bud is formed above the 

 origin of the primary root, between two of the primary leaf- 

 traces. At this time there are already developed three or more 

 leaf-whorls about the shoot-axis. The second shoot does not 

 develop its first root until its first foliar sheath is well developed. 



In most species that have been studied, the primary shoot 

 has the leaves of the whorls in threes, but in E. variegatiim 

 (Buchtien (i), p. no) there are regidarly but two leaves in 

 each whorl, and Jeffrey found that this was sometimes the case 

 in E. limosum. 



The development of the primary axis, unlike that of the 

 Filicinese, is limited, and it ceases growing after producing ten 

 to fifteen sheaths, which, like the first one, are three-toothed. 

 The stem remains very slender, but shows the marked division 

 into nodes and internodes found in the later ones. This pri- 

 mary stem has irregular lacunae in the cortex, but does not show 

 the cavity so conspicuous in the central part of the older plant, 

 and in E. tcUnatcia, according to Buchtien, this is quite solid. 

 In this species he figures four vascular bundles, whose xylem is 

 relatively much better developed than in the later stems. The 

 bundles, like all of those in the stem and leaves, are collateral, 

 and the whole group is surrounded by a well-marked endo- 

 dermis. From the base of this primary shoot a second stronger 

 one develops. This second shoot is much more vigorous, and 

 its leaf-sheaths have four teeth. From the base of this others 

 arise in the same way and in rapid succession. Sometimes the 

 third, or one or more of the later formed basal shoots, bends 

 downward and penetrates the earth, producing the first of the 



