NOTES ON RECENT RESEARCH. 



1109 



region. Both the micropylar and chalazal regions of the embryo-sac are 

 very rich in food material. The author did not find that the antipodal 

 cells divide. There is a full account of the nuclear divisions observed, 

 and a short description of the seed. There are five figures in the text. 



G. F. S.-E. 



Embryos of Dicotyledons, Observations on the Development 



Of. By B. Schmid (Bot. Zeit. parts 10 and 11, pp. 207-230, Nov. 1, 1902 ; 

 with 3 plates). — A record of observations on the varying development of 

 the embryo, and especially on partial or entire abortion of one of the 

 cotyledons on some plants, which, though undoubtedly belonging to 

 dicotyledonous orders, consequently resemble monocotyledons in the 

 primary stage. — C. T. D. 



Causes of Leaf-fall in Ceylon. 



Foliar Periodicity in Ceylon. Note by Herbert Wright, Peradeniya 

 (Ann. Bot. vol. xvi., No. 64, p. 595). Abstract of paper read before 

 Section K of the British Association, Belfast, 1902. — " The high tempera- 

 ture and humidity of the air in most parts of Ceylon allow almost con- 

 tinuous growth of the arborescent vegetation. There are, however, nearly 

 two hundred species which become leafless at different times of the year. 

 External and internal factors affect the phenomena of defoliation and 

 foliar renewal. The climatic effect is obvious from the fact that the 

 majority of our deciduous species become leafless during our hottest and 

 driest months. The deciduous trees respond only to one hot dry period 

 of three or four months, and not to the dry part of each monsoon. Some 

 species undergo complete defoliation twice per year ; these exhibit 

 periodic increase in foliar activity several times per year, in addition to a 

 complete annual renewal, and many introduced species show great varia- 

 tion during their phase of acclimatisation. In the northern districts, 

 where the rains of the south-west monsoon are very feeble as compared 

 with those at Peradeniya, the defoliation is considerably delayed. The 

 climatic conditions in Ceylon are not equable enough to allow continued 

 development along personal lines, and botanists desiring to study the 

 personal equation in plant-life should select a more equable area. Internal 

 forces are, however, obviously at work, as evidenced by the following 

 facts : — 



" (a) Species retain full possession of their foliage or put forth new 

 leaves when the temperature and dryness of the air are at a maximum. 



" (b) Some species drop their leaves and remain bare during our wet, 

 cool months, when transpiration is at a minimum. 



" (c) Plants of the same species, on the same plots, are deciduous at 

 periods varying by many weeks and months. 



" (d) The same species may undergo defoliation at approximately the 

 same time of the year, though under the dissimilar climates of Peradeniya, 

 Colombo, and Manaar. 



" The irregularity of foliar periodicity is very pronounced. There is not 

 a month when all the trees are in full leaf. The foliar periodicity of the 

 evergreens is as complex as that of the deciduous trees ... all being 

 subject to individual variations. Foliar periodicity is the most potent 



