I909 ] CURRENT LITERATURE 337 



Although no explicit statement is made, the reader is apparently left to infer that 

 there are two modes of origin of a hollow stele: (i) one in which the central trach- 

 eidsare replaced by parenchyma (Schizaea), (2) one in which fundamental tissue 

 passes into "pockets" at the leaf gaps and becomes continuous with the tissue 

 in contiguous pockets (Alsophila\ Although the latter view of the origin of 

 "pith" is essentially that of Jeffrey, no mention of the fact is made in the text, 

 but such reference is relegated to the preface, where the author disclaims adher- 

 ence to this view. The evolution of solenostely into dictyostely, and finally into 

 polycycly is clearly traced, and the complicated condition found in Marattiaceae is 

 adequately illustrated by diagrams from various sources. 



Concerning the Osmundaceae, the conclusion is reached that the stele does 

 not represent a reduced type, but shows a gradual progression from the condition 

 seen in Botryopterideae, from which group the Osmundaceae have probably 

 been derived. The recent work of Kidston and Gwynxk-Vaughan on fossil 

 members of the group is quoted in defense of this position. 



In a succeeding lecture the evolution of the leaf-trace is outlined, and it is 

 shown that elaborations of the primitively simple curved trace follow upon 

 increase in the leaf-surface, and in turn bring about increasing complexity in the 

 central cylinder of the stem. According to the author's view "the leaf-trace leads, 

 and the stele follows, in the course of evolution." The ontogeny of the vascular 

 system is next summarized, and a final lecture is devoted to a comparison of the 

 vascular system of various phyla. The criticisms of Jeffrey's primary groups 

 Lycopsida and Pteropsida have already been dealt with in this journal 2 .— M. A. 



Chrysler. 



The American Breeders' Asssociation 

 The fourth annual report of the American Breeders' Association' is, in a num- 

 ber of features, a decided improvement over previous volumes. The same high 

 standard of matter is maintained as in previous reports, but there is more of it. 

 !t 's printed on better paper; and contains numerous fine half-tone engravings. 

 L'nlike many publications which are more or less influenced by practical con- 

 'derations, the articles presented in the reports of the American Breeders' Asse- 

 rtion appear to suffer no diminution of scientific value because of the large 

 contingent of practical breeders among its membership and on its programs. 

 Almost every phase of practical and theoretical breeding of plants and animals. 

 55 *ell as two interesting reports upon eugenics, the new science of improvement 

 of the human race, are inclu'ded. Papers of importance from the standpoint 

 of the practical plant-breeder include several upon the production of disease- 

 r stance in various plants by W. A. Orton, P. K. BMW, and H. L. Boixe\ , 



•JtWWW, E. C. Are there foliar gaps in the Lycopsida? Box. (Iazette 

 *:*4i-258. ph. , 7 , l8 . IO o8. 



3 Report of the American Breeders' Association. Vol. IV. pp. 373- #*• * 

 fi K s -74- 1908. 



