BOOKS AND CURRENT LITERATURE 141 



entirely of leaf traces, fused with each other, and with those of the root 

 and cotyledon, but without any trace of cauline elements, coming from 

 the plerome of the stem apex. This fact strengthens the conclusion that 

 the young plant is made up, primarily, of root and cotyledon only. In 

 a fourth section of Part I it is shown that the same mode of origin of the 

 vascular system is found at the apex of the mature stem. A true cam- 

 bium is present in the stem of Botrychium, even when but five or six 

 leaves have been developed. The fertile portion of the sporophyte 

 Campbell regards as a structure sui generis, or sporangiophore, as was 

 suggested by Bower, and does not admit that it can be the equivalent 

 of one, or two, fused pinnae, as held by Goebel and by Chrysler. In 

 studying the development of the leaf Campbell finds that the fertile and 

 sterile portions arise by a dichotomy of the leaf rudiment. The vascu- 

 lar system of the spike arises from parts of two bundles, the remainders of 

 which continue on to form parts of the vascular system of the sterile 

 blade. 



In Part II Campbell discusses, in the same detailed manner, the game- 

 tophyte, embryo and mature sporophyte of Marattia, Danaea and Angi- 

 opteris. He notes the occurrence in the green prothalli of these forms of 

 a mycorrhiza, similar to that in the subterranean prothalli of the Ophio- 

 glossaceae. The sexual organs are found to be similar to those of the 

 latter family, as is the spermatogenesis, which was studied in Danaea and 

 Kaulfussia. In the development of the embryo the root arises second- 

 arily, and it, as well as the stem and cotyledon, is derived from the epi- 

 basal half of the oospore, probably from the same octants as the cotyle- 

 don. The vascular system of the very young plant consists of fused 

 leaf traces only. In a plant of Danaea jemnani with seven leaves, a 

 commissural strand had appeared, which is derived directly from the 

 plerome of the stem apex. This small commissural strand is developed, 

 at this time or later, in all the Marattiaceae studied. In this study of 

 the vascular system one could wish that every possible means had been 

 taken to locate the elusive endodermis, because of its value as a definite 

 boundary line. The peculiar groups of sporogenous cells arise, in con- 

 trast with those of the Ophioglossaceae, on little modified leaves. Camp- 

 bell rejects the view that the latter have arisen by the fusion of the fer- 

 tile and sterile portions of a leaf like that of Ophioglossum. He suggests 

 that the sporophylls of the Marattiaceae may have arisen by the gradual 

 sterilization, extension and flattening of part of the tissue of a sporangio- 

 phore, as sometimes occurs to a striking degree in Helminthostachys. 

 In spite of the differences in the sporophylls there are many features in 



