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 in 

 Ceylon at about i,8co 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 they produce young leaves and flowers. More precise 

 observations on these interesting phenomena are not available. 



3. PERIODICITY IN THE SEXUAL DOMAIN. 



i. GENERAL CONSIDERATIONS. 



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

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

 herbaceous plants, devoid of tubers or bulbs, vigorous development of the 

 reproductive organs is generally attained only after the foliage has been 

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

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

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

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

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

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

 reserve-material. This precedence of flower seems to occur frequently, 

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

 caulifiorous plants. 



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

 especially in woody ones, stretches over two periods separated by a season 

 of rest, the first period being one of inception, and the second, one of growth. 

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

 following remarks therefore concern only the later stages of development 

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

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

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

 below is therefore merely fragmentary. 



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

 external influences on the development of flowers are more clearly revealed 

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

 reproductive functions on the assimilatory activity of the foliage interferes 

 with the expression of any such external influence. 



