158 THE MARATTIALES 



may usually be recognized without difficulty. This cell is usually quite deep and 

 in all of the genera except Dancra has a truncate base in longitudinal section. In 

 Dancea, however, the base is usually pointed and the cell closely resembles the corre- 

 sponding cell in Botrychium, or the typical leptosporangiate ferns. The growth of 

 the stem is usually rather slow and the leaves of the young plant are much crowded. 



In all of the forms examined, the tissue derived from the inner cells of the 

 segments and from the basal segments of the apical cell, where such segments were 

 formed, remained as undifferentiated parenchyma and contributed only to the 

 internal pith of the stem. Except that the leaves arise from the segments of the 

 apical cell of the stem and all of their tissues are therefore indirectly derived from it, 

 the stem apex of the young sporophyte takes no part at all in the development of 

 the fibrovascular system of the stem, which, except for the bundles of the roots, is 

 entirely composed of the leaf traces. 



The second leaf in Angiopteris usually shows a pretty well-defined but slender 

 midvein, which may, however, fork at the apex, and this is true also of the third leaf. 

 It is in the third leaf, both in Marattta and Angiopteris, that the characteristic 

 stipules are first developed. These appear as lateral wing-shaped bodies close to the 



Fig. 143. 



A. SecdoD of primary root of Danaa jamaicensis. X70. 



B. The vascular bundle. X175.' en, endodermis. 



C. Triarch bundle from a primary root of D. elliptka. 



base of the petiole, partially inclosing the next youngest leaf and the stem apex. 

 The third leaf in Angiopteris and several others succeeding it assume a more and 

 more pronounced lanceolate form with a prominent midrib and pinnately arranged 

 lateral veins which usually fork once. The margin of the leaf is serrate. After 

 several of these lanceolate leaves have been developed, leaves are formed in which 

 the base is provided with auricles, and these gradually pass into the next type of leaf, 

 which is ternate, the terminal leaflet being very much larger than the lateral ones 

 (plate 13, figs. 4, 5). These ternate leaves then pass by intermediate stages into 

 the pinnate form of the leaves of the adult plant. 



In Kaulfussia the second and third leaves closely resemble the primary one, 

 except that they are somewhat larger (fig. 123). The second leaf develops well- 

 marked stipules which are found in all of the later leaves. The earlier leaves do not 

 show a definite midrib, though there is usually a delicate midvein at the base of the 

 lamina, but this vein forks usually about half-way up. In the older leaves (fig. 123, 

 C) there is developed a stout midrib, from which extend distinct pinnately arranged 

 lateral veins, much as in Angiopteris, but these lateral veins are connected by a 

 system of anastomosing veins, so that the leaf most strikingly resembles that of a 

 typical Dicotyledon. It is not until a very late period that the leaves in Kaulfussia 

 assume the compound form of the older plant (plate 11, fig. i). 



