200 THE MARATTIALES 



formed just opposite where the second leaf trace joined the stele. The apical cell, 

 which had apparently developed from an endodermal cell, had only undergone the 

 first division. This root was probably not the first lateral root, or if it was, it had 

 formed very much later than is usual. The base of the plant had been somewhat 

 injured and there was what looked like the remains of another root, which was 

 probably the first lateral root. 



The oldest specimen of which sections were made had four fully developed 

 leaves and the rudiments of the fifth and sixth. An examination of the lower series 

 of sections showed the remains of one or two other leaves and it was probable that 

 eight leaves all together had been formed. At the level of the stem apex (fig. iSi,B) 

 six separate leaf traces could be seen and the relation of the younger ones to the apex 

 was exactly the same as in the younger sporophyte. Below the apex, the central 

 stele of the stem shows a broken ring of procambium inclosing larger parenchyma, 

 representing the pith. The procambium ring is made up evidently of two portions, 

 one of which is certainly referable to the sixth leaf trace, while the opposite one 

 perhaps represents the beginning of the next leaf trace, although the leaf to which 

 it belongs is not yet evident above (fig. i8i, D). The junction of the leaf traces so 

 close to the stem apex makes this point very difficult to decide. 



The fusion of the fifth and fourth traces follows quickly and the resulting stele 

 shows plainly the three separate xylems of its component bundles. The older 

 portion of the stele shows that it is still solid, with no evident leaf gaps (fig. i8i, 

 E-G), but with several groups of tracheids probably corresponding to as many leaf 

 traces, though less distinct than in the younger plant. This is complicated by the 

 fusion of the root traces, which disturbs the arrangement of the xylems from the 

 leaf traces, but the xylem is less compact than is figured by Farmer and Hill and 

 the "pith" much less definite; indeed, one can hardly speak of a pith in this connec- 

 tion. No trace could be seen of the central commissural strand which later makes 

 its appearance and which presumably arises in the same way that it does in Danaa. 



In the early stages Angiopterts appears to agree closely with the other Marat- 

 tiaceae in the development of its vascular system, but the single central stele without 

 leaf gaps is retained much longer than in the other genera and it also becomes much 

 larger and has a better-developed xylem, and the open dictyostele, formed from the 

 anastomosing of the early single leaf traces, characteristic of Dancea and Marattia, 

 is not present. It is not quite clear whether the "siphonostele" with its small leaf 

 gaps, which is the next stage in the development, is made up entirely of leaf traces, 

 and it is possible that the stelar tissue, connecting the adjacent leaf traces, may be 

 composed in part of cauline tissue. On the other hand, it is quite as likely that the 

 connection of the leaf traces is brought about merely by a broadening at the point 

 of contact, such as occurs in Helminthostachys. Indeed, at this stage, the stele of 

 Angiopteris is more like that oi Helminthostachys than like that of the other Mafat- 

 tiaceae. 



THE ADULT SPOROPHYTE OF ANGIOPTERIS. 



In habit Angiopteris closely resembles the larger species of Marattia. The 

 enormous leaves are arranged spirally about the thick upright caudex, which is 

 covered completely by the persistent bases of the old leaves. The leaves are usually 

 twice-pinnate; the linear leaflets have more or less conspicuously serrate margins 

 with a venation very much like that of Dana a, the veins being more closely set than 

 in Marattia. In addition to the ordinary subterranean roots, large aerial roots are 

 not infrequent, but it is doubtful if there is any essential difference between the two 

 kinds of roots. 



