CURRENT LITERATURE 



BOOK REVIEWS 



Evolution of the filicinean vascular system 



Professor Tansley 1 has done well to gather under one cover his lectures on the 

 vascular system of ferns, previously published in the New Phytologhi. The 

 attempt is made "to gather together the results that have accrued from the 

 researches on the morphology of the vascular system of ferns which have been 

 undertaken during the last few years, and to present these results from an evo- 

 lutionary standpoint." The first lecture discusses various theories which have 

 been advanced to account for the origin of the main phyla of Pteridophyta. The 

 author favors the view of a direct derivation from Algae in which an alternation 

 of generations had already been established. Accordingly, the sporophyte of 

 pteridophytes would not correspond to that of bryophytes, in which an antithetic 

 alternation of generations seems to have been worked out. The author admits 

 that the presence of an archegonium in both mosses and ferns is an obstacle to 

 this view. Assuming a monophyletic origin for pteridophytes, the view is advanced 

 that the ancestral form was one with a radially organized axis having branches, 

 some of which became specialized as leaves. These leaves were relatively lar 

 and appear to have branched dichotomously; hence the derivation of Fthcales 



is not credited. It is even suggested that small-leaved 

 forms, such as Lycopodium, may have been derived by reduction from mega- 

 phvllous ancestors. The whole scheme of phylogeny proposed is largely specu a 

 tive, but such attempts will be welcomed by those who find difficulty in accep in 

 Bower's well-known hypothesis. . 



In the second lecture the Botryopterideae are reviewed, and much sea e 

 information on this group is rendered available. Proceeding from the P ro 

 condition exhibited by Grammatopteris, the complications shown by Z ?°^ 

 and other genera are discussed, and the conclusion is reached that t g ^ 

 stands near the ancestors of the different phyla of fern-like plants. - mong ^ 

 Hymenophvllaceae the mode of exit of the leaf-traces lends suppo ^^ 

 author's view of the identical nature of leaf strand and stem stele. ^ 



>'ng this family, as well as the Gleicheniaceae and Schizaeaceae, Boodl . 



form 



upon and is presente 



rolutionary standpoint. 



logeny as indicated by the stele is compared with that inferred from F"^ 



gia, and a general correspondence is claimed, though the latter en e 



sidered to be the more reliable. . honoS tele) 



In the sixth lecture the evolution of a protostele into a solenostele (sip ^, 

 is considered with reference to the examples found in the foregone 



• Tansley, A. G., Lectures on the evolution of the filicinean yascu a^ ^^ 

 New Phytologist reprint no. 2. Paper. 8vo. pp. M4- Cambridge. 



1908. 38s. 6rf 



336 



