ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 269 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Structure and Development. 

 Vegetative. 



Evolution of Eucalyptus.* — C. Hall has studied the cotyledons of 

 a number. of species of Eucalyptus in special relation to the evolution 

 of the genus. The results of the author's investigations confirm those 

 obtained by Baker and Smith as the result of chemical and botanical 

 research. The Corymbosas must be regarded as the most primitive 

 group, and they were derived from an ancestor having comparatively 

 large entire reniform cotyledons. Necessity for adaptation to environ- 

 ment brought about reduction of leaf -surf ace, as seen in E. trachyphlaia 

 and other species. The Stringybarks appear to have arisen as an 

 offshoot from the Corymbosas, and owing to similar causes developed 

 small cotyledons and hairy primary leaves. The origin of emargination 

 is difficult to trace, but E. Planchoniana and E. marginata may repre- 

 sent descendants of the earlier examples. The cotyledons and primary 

 leaves of the former point to its being a transition form to the Pepper- 

 mints and their allies. The emarginate globulus type is usually accom- 

 panied by reduction in size of the cotyledon, but in West Australia the 

 exceptional dryness of habitat has brought about a specially adapted, 

 deeply bifid form of cotyledon, which has now spread to South and East 

 Australia. Change in the form of cotyledon has been accompanied by 

 change in essential oils. The corymbosa type of cotyledon is associated 

 with pinene oil without eucalyptol. The members of the Peppermint 

 group contain eucalyptol, phellandrene, and piperitone in varying pro- 

 portions. The globulus type is characterized by eucalyptol-pinene oil, 

 and in the more reduced types aromadendral. The bifid cotyledon is 

 found associated with eucalyptol, pinene, and aromadendral. Finally, 

 the author points out the great importance of Eucalyptus in the study 

 of evolution, since so many of its connecting links appear to have 

 survived, and it is now possible to trace the important part played by 

 the cotyledon. 



, Growth-studies in White or Weymouth Pine (Pinus Strohus).t 

 H. P. Brown, who has previously studied the growth of a hard pine. 

 Pinus rigida, now gives the results of his study of a soft pine, P. Strobus. 

 He finds that the winter condition of the secondary cortex and cambium 

 is similar to that of P. rigida. The marked differences which occur 



* Proc. Linn. Soc. New South Wales, 1914, pp. 473-532 (32 pis.). 

 f Bot. Gaz., lix. (1915) pp. 197-241 (2 pis.). 



June Will. J9J-5 u 



