216 THE BOTANICAL MAGAZINE. [V oi. xxiv. m. 2 S4 . 



with the remarkable capacity of pollination of Ginkgo, in which 

 the two sexes may be apart even as far as 500-1000 meters 

 or much more. Here among other things the great height of 

 the tree, its copious branching with rich production of flowers, 

 and the exposed condition of ovules may be of some advantages. 



Unlike Conifers, Ginkgo is a plant similating in some respects 

 the habits of Angiosperms. Yet it shares w T ith all other Gym- 

 nosperms the primitive habit of anemophily. We do not know 

 how wind blew in the Mesozoic and other geological ages. 

 Certainly the wind condition is an important factor for the 

 pollination of the anemophilous plants. In this respect plants 

 of the habit of forming a thick ' pure forest ' have a much 

 greater chance of pollination than those which form a loose or 

 ' mixed ' one. The appearance of Angiosperms and their inter- 

 vening or intermingling may have been an event not to be 

 forgotten in the history of decline of some Gymnosperms. 



Yendo (K. Yendo, 1909. "The Sun." vol. XV. No. 7) holds 

 the view that the great success of modern Angiosperms and of 

 Insects among animals is chiefly due to their mutualism in the 

 pollination of flowers. The 'pure fo.est ' or flora is certainly 

 the primitive type of vegetation, from which the 'mixed' ones 

 have been derived ; and the habit of entomophily will be one of 

 the most favorable conditions for the successful existence of a 

 'mixed ' complex flora, and the failure of a plant in the acquisi- 

 tion of this habit may have led to its decline. 



Groom (P. Groom, 1910. Ann. of Bot. XXIV.) is of the 

 view that the defeat and extinction of many Conifers in past 

 ages may be at least partially attributed to their greater 

 vulnerability and smaller powers of repairing injuries than 

 dicotylous trees. How much stress can be laid on this point 

 must be seen by a further study. At present it may only be 

 noted that the Dicotyledons selected by Groom for comparison 

 with Conifers, all but Fraxinus, belong to Archichlamydese, 

 many of the members of which turn out as fossils at present, 

 and may probably be following the fate of Conifers. 



An opinion, that species get old and weak with age and 

 die away, just as individual organisms are subject to certain 



