102 BOOKS AND CURRENT LITERATURE 



spermous seeds and in this there are many things to take exception to, 

 although the parts describing the results of the morphological investi- 

 gations of the British and French students of petrified materials are, 

 on the whole, very well done. The remainder of the book is taken 

 up with the description of fossil Cycadophytes. These are very well 

 handled and give a satisfactory summary of the present state of our 

 knowledge, although the concluding chapter, that dealing with the 

 frond genera, is much abbreviated and not especially^ noteworthy, as 

 I have already remarked. 



Unless one reads with discrimination one will gather the idea that 

 the Mesozoic flora was dominated by plants of the type of Cycadeoidea. 

 This is rather wide of the mark. The Cycadeoideas are significant 

 chiefly because their wonderful preservation has enabled Wieland 

 and others to unravel the details of their structures so that they have 

 become the key to our understanding of Mesozoic Cycadophytes. 

 They are probably less important from a phylogenetic standpoint than 

 such forms as Wielandella or Willia7nsoniella. It is moreover extremely 

 doubtful if the Cycadeoideas were ever much more of a dominant 

 element in the Mesozoic floras than are the existing cycads in the 

 Recent flora. They represented a very much specialized side-line with- 

 out issue, while the really important Cycadophytes of the Mesozoic 

 were those forms which Wieland has grouped together under the name 

 of the Williamsonia tribe. In these, while the fructifications were 

 morphologically like those of Cycadeoidea, the habit was very dif- 

 ferent, and it is these forms that approach the ancestral Pteridosperms 

 on the one hand, and types like the Ginkgoales on the other. It seems 

 probable that the bulk of the frond genera belonged to the William- 

 sonias rather than to the Cycadeoideas. Seward is hardly justified 

 in doubting the bisexual character of the so-called flowers of Cycadeoidea 

 Gibsoniana, nor is it easy to follow him in his explanation of the sup- 

 posed corona of Williamsonia gigas as, morphologically, a whorl of 

 connate stamens in a central terminal position. When it is remem- 

 bered that throughout all of the Cycadeoidea species already inves- 

 tigated the megasporophylls become more or less sterile distad and 

 that in some species, as Wieland has demonstrated, these, together 

 with the prolonged interseminal scales are modified to form a mop-like 

 tuft at the apex of the receptacle, and also having in mind the ears 

 or wings of the microsporophylls that formed a canopy over the 

 apex of the receptacle in Cycadeoidea colossalis, it is quite possible 

 to explain Seward's figures 546 and 547 in a variety of ways with- 



