590 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Reference is also made to the " recapitulationary confirmation of the 

 principle of evolution," which has been brought to light by anatomical 

 investigations, and it is shown how such recapitulationary evidence 

 confirms the opinion as to the primitiveness of the " breech-fertilised " 

 Amentiferae. Finally, the author briefly mentions how the views set 

 forth by anatomists as to the position of the Cycadofilices have been 

 fully confirmed, and urges the importance of continued investigation of 

 internal morphology. 



Recent Advances in Vascular Anatomy.* — J. M. Coulter con- 

 tributes a paper upon the recent advances made in the study of vascular 

 anatomy, especially that of the reproductive structures. The present 

 work is a brief resume of the modern views of vascular anatomy, as 

 based upon an evolutionary basis. It is shown that the old idea as to 

 certain great groups of plants having been derived from other existing 

 groups, is no longer tenable. The discovery of the Pteridosperms has 

 shown the improbability of the descent of the Gymnospernis from the 

 Ferns, although modern ferns may illustrate stages in the evolution of 

 Gymnosperms. Recent discoveries on the history of the Gymnosperms 

 show that they originated from fern-like plants bearing microsporangia 

 and megasporangia, and that a strobilus was gradually evolved. The 

 Cycads retain more primitive characters in their sexual reproduction and 

 vascular system, while the Cordaitales have developed a more advanced 

 vascular system which is continued in Ginkgoales in one direction and 

 Coniferales in the other. It is especially to be noted that primitive 

 features cannot be regarded as a mark of age unless history confirms 

 their testimony. Finally, after a brief allusion to the modern con- 

 ception of the monocotyledons as " a specialised offshoot from the 

 primitive dicotyledonous stock," the writer draws attention to the need 

 of the combination of several investigators upon one problem, where 

 the latter entails great labour, and is important enough to justify such 

 a united effort. 



Reproductive. 



Pollen of Microcachrys tetragona.f — R. B. Thomson has examined 

 the pollen-grains of Microcachrys tetragona, and finds that they are 

 small and have two to six wings, which arise in the usual way. The 

 wings arise late, thus giving evidence of recent acquirement. Four 

 prothallial cells are often present, but three is the more usual number. 

 The structure of the gametophyte agrees with that ascribed by recent 

 investigators to allied forms. The character of the wings places 

 Microcachrys intermediate between Saxegothsea on the one hand and 

 Dacrydium and Podocarpus on the other. The author finds no reason 

 for regarding the wing-formation as indicative of affinity between the 

 pines and podocarps, and hopes later on to show essential differences in 

 the character of the megasporophylls of these two great phyla of 

 Conifers. 



* Amer. Nat., xliii. (1909) pp. 219-30. 



t Bot. Gaz., xlvii. (1909) pp. 26-9 (2 pis.). 



