248 ZONES AND REGIONS [Pt. Ill, Sect. I 



at its base, in summer-condition at its summit ; a larger plant of the same species 

 displayed on some branches light-red vernal tints and dark-red autumnal ones, 

 whilst others were bare as in winter. Amygdalus communis was in purely 

 spring attire. 



In less uniform tropical climates, the periodic phenomena of woody plants 

 coming from the temperate zones seem to adapt themselves to the new seasons. 

 Then the phenomena naturally occurring in winter and spring take place in the' 

 dry season, and those characteristic of summer and autumn come to pass in the 

 rainy season. Mr. Nock, the Curator of the experimental garden at Hakgalla inj 

 Ceylon at about i,8oo meters above sea-level, told me that European trees lose most! 

 of their foliage during the wet south-west monsoon, whilst during the moderately 

 moist autumn months thej' produce young leaves and flowers. More precise 

 observations on these interesting phenomena are not available. 



3. PERIODICITY IN THE SEXUAL DOMAIN. I 



i. GENERAL CONSIDERATIONS. 



In the majority of plants, flower and foliage exhibit a certain antagonisn 

 and are usually separated in their development in time or in space. Ir 

 herbaceous plants, devoid of tubers or bulbs, vigorous development of th( 

 reproductive organs is generally attained only after the foliage has beat 

 completely or almost completely formed. In this case, at all events, on 

 may interpret the phenomenon by ascribing to the foliage the work o 

 forming nutritive material for the production of flowers and fruits. In th 

 case of plants with rhizomes, and of woody plants, there is no such direc 

 dependence, and we see in fact the formation of flowers often precedini 

 that of foliage, when it takes place at the expense of the previous year' 

 reserve-material. This precedence of flower seems to occur frequentlj 

 when flower and foliage are at some distance from one another, as i 

 cauliflorous plants. 



In zones with cold winters, the development of blossom in many plant 

 especially in woody ones, stretches over two periods separated b)' a seaso 

 of rest, the first period being one of inception, and the second, one of growtl 

 It is not known to what extent this also occurs in the tropics. Th 

 following remarks therefore concern only the later stages of devclopmet 

 that are easily discernible by the naked eye. Flowers have received fc 

 more attention than have fruits, as the former have been more minutel 

 investigated by earlier observers as well as by myself. What is state 

 below is therefore merely fragmentary. 



Woody plants may be considered in the first place, as in them an 

 external influences on the development of flowers are more clearly reveak 

 than in most herbaceous plants, in which the direct dependence of tl 

 reproductive functions on the assimilatory activity of the foliage interfen 

 with the expression of any such external influence. 



