54 



THE JOURNAL OF BOTAXT 



features of plant evolution emerge. As in previous editions, the 

 illustrations form a noteworthy feature of the book, and many new 

 and beautiful figures are included in this edition. 



Twelve years have elapsed since the publication of the second 

 edition, and during that period several noteworthy advances have been 

 made in our knowledge of the Palaeozoic Pteridophyta. Some of them 

 have helped to fill up gaps in the long continued researches on such 

 familiar plants as Catamites and Sphenophyllum. In other cases 

 work, such as that of Kidston and Grwynne-Vaughan, of Bertrand and 

 of Gordon on the older Ferns, has not only increased the store of 

 knowledge, but has cleared up uncertainties and provided a fund 

 of authentic information, which enables us to reconsider some evolu- 

 tionary theories maintained in former days without much positive 

 evidence. To those who have not had the opportunity of studying 

 the original papers, the brief sketch given here, with admirable i'llus' 

 tration, of the past history of the Osmundaceaj, must prove of 

 considerable interest; as also of that remarkable group of Paleo- 

 zoic ferns, the Zygoptendese, with their curious petioles and two- or 

 four-ranked pinna? which do not seem to have developed the flattened 

 laminae now characteristic of leaves. 



But it is the last and entirely new chapter in the volume to which 

 all botanists will turn with eagerness. Many of us will begin the 

 book by reading first this last chapter ; and we may be excused, for it 

 contains an account of the earliest known Devonian land-plants. 

 It is the first full and illustrated summary yet published by an 

 independent expert, of Kidston and Lang's work on those most 

 remarkable genera, Bhynia, Hornea, and Asteroxylon— work which 

 must be regarded as one of the most important' contributions yet 

 made towards our knowledge of plant evolution. In recent years 

 some of us have almost despaired of finding any definite evidence of 

 really early and generalized fossil plants. We seemed to have in the 

 Lower Carboniferous and Upper Devonian rocks highly-evolved types 

 of Ferns, Lycopods, and Pteridosperms, nearly as complex as those 

 varied types of Upper Carboniferous age. But now in the Psilo- 

 phytales we have plants of a very simple type— leafless, rootless, with 

 the simplest of vascular tissue, with the simplest sporangia, and much 

 more like the primitive plants which we may have imagined. And 

 moreover, these forms are not known from blurred impressions or from 

 isolated fragments, but from petrified examples whose preservation is 

 most perfect, whose stems give sections as fine as if cut from a recent 

 plant, displaying such features as the stomata, rhizoids, and mycorhiza. 

 It is almost incredible that the simplicity of these forms should be due 

 to reduction following the adoption of the mycorhizal habit, and we 

 may have to revise our ideas upon the early evolution of plant- 

 structures. Some theories of which little has been recently heard, 

 such as Treub's? "protocorm" theory, may once more come into 

 prominence, and Lignier's views on the morphology of stem and leaf 

 will have to be given fresh consideration. 



It is interesting to notice that Dr. Scott is favourable to the ideas 

 which Dr. A. H. Church has recently put forward, and it may be that 

 the discoveries of these most ancient plants will awaken a fresh 

 interest in the study of the morphology of the marine algaa of the 



