434 MOSSES AND FERNS chap. 



stem of the young sporophyte. After one set of lateral 

 segments has been cut off from the root quadrant, the primary 

 cap cell is formed as in the Ferns. Unlike the latter, the 

 divisions in the stem apex proceed rapidly, and it soon projects 

 in the centre of the embryo as a broad conical prominence^ 

 terminating in the large tetrahedral apical cell. 



The three parts of which the primary leaf- sheath is com- 

 posed remain distinct and form the three teeth (Fig. 226, C), 

 which grow rapidly until they are about on a level with the 

 apex of the stem. This growth is mainly due to the activity 

 of the marginal cells. The root grows less actively at first 

 than either stem or leaves, and at the time the latter is nearly 

 fully developed forms but a small protuberance at the base of 

 the embryo (Fig. 226, C). The foot at this time is not 

 conspicuous, 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 next rapidly elongates and grows 

 upward through the calyptra. The embryo thus perforates the 

 prothallium both above and belov/, as in Marattia, although 

 owing to the position of the archegonium in the former the 

 relation of the embryo to the latter is not the same. 



Hofmeister states ^ that the vascular bundles are not formed 

 until after the primary organs have broken through the pro- 

 thallium, but this point needs further examination. 



The development of the primary axis, unlike that of the 

 Filicineae, 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 

 primary stem has irregular lacunse in the cortex, but does not 

 show the cavity so conspicuous in the central part of the older 

 plant, and in E. telmateia, 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 endodermis. From the base of this primary shoot a 



^ Hofmeister (i), p. 303. 



■^ Buchtien states that in E. variegatum they are only two-toothed. 



3 Buchtien (i), Fig. 119. 



