THE YOUNG SPOROPHYTE 81 



The primary root, as Lang pointed out, is usually triarch, but occasionally 

 diarch roots occur, as they usually do in Botrychium and in Ophioglossum pendu- 

 lum. In this case, however, one of the xylems was rather larger than the other. 

 The later roots are tetrarch and in the older sporophyte, as Farmer showed, the 

 roots generally have six xylem masses, or occasionally seven. This type of root is 

 most like that of the Marattiaceae. The endodermis is pretty well developed, but 

 not so conspicuous as it is in Botrychium. 



In the cortical region of the first root there is a zone of cells in which occurs an 

 endophytic mycorrhiza, such as is common in the roots of other Ophioglossaceas, 

 and probably the same as the endophyte which is found in the tissue of the prothal- 

 lium. Whether the infection of the primaiy root is direct from the prothallium or 

 whether there is a new infection from the soil was not determined. Lang states 

 that the mycorrhiza is only developed in the first two or three roots, the fourth root 

 and those formed later not having the endophyte. In these later roots the cortical 

 cells are densely filled with starch. 



The rhizome continues to grow upright for a good while and it was not deter- 

 mined at just what time it assumes the prostrate position which it has in the adult 

 form. At first there is usually one root formed for each leaf, but in the older plants 

 this regularity is lost, and Farmer states that there may be three or four roots 

 developed for a single leaf. On the other hand, the number of roots may be less 

 than that of the leaves, especially in the younger plants. 



A curious abnormal form was seen in a young sporophyte, where for some reason 

 several of the earliest leaves had remained in the rudimentary condition of the cotyle- 

 don. Five of these rudimentary leaves could be seen formed in succession. The 

 sheaths were fully developed and there was a long internode between each pair of 

 leaves. Three of these had developed roots, but the others had failed to do so. This 

 rhizome was nearly 3 centimeters in length, but it had hardly increased at all in 

 thickness. A single ternate leaf had expanded at the summit, but whether this 

 was the first functional leaf that the plant had developed could not be determined, 

 as the rhizome was broken off below and there may have been one or more func- 

 tional leaves developed below the first of the rudimentary ones. 



This repetition of vestigial leaves recalls the condition of things in Ophioglossum 

 vulgatum and Botrychium lunaria. For a good while the new leaves are of the same 

 ternate form as that of the first foliage leaf, but sooner or later, probably depending 

 on the vigor of the plant, the ternate form is gradually replaced by five foliate leaves, 

 the later divisions being the result of an unequal dichotomy of the lateral leaf seg- 

 ments, similar to that by which the second lateral segments of the primary leaf are 

 separated from the terminal leaflet. In these five foliate leaves the characteristic 

 "pecopterid" venation of the adult sporophyte is fully attained (fig. 45, B). Each 

 lateral vein forks twice, the ultimate veinlets extending to the margin of the leaflet. 

 A section of the petiole of one of these leaves shows that it contains four vascular 

 bundles, arranged in pairs. The dorsal bundle of each pair is decidedly larger than 

 the ventral one. The base of the petiole is almost perfectly cylindrical, but further 

 up it becomes winged, so that a groove appears on its inner face extending for some 

 distance below the junction of the lamina and the petiole. There is a very slightly 

 developed hypodermal tissue composed of two or three layers of cells, the walls of 

 which are colorless and considerably thickened, some of them showing thickened 

 corners like the collenchyma found in the leaves of the Marattiaceae. 



