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



In the cases described above all the parts of the crown of the tree 

 exhibited the same behaviour. In other cases individual twigs shed their 

 leaves and acquire fresh ones at different times. I have observed this in 

 tropical trees only in connexion with the flowering time, and will therefore 

 not discuss the matter till later on. 



ii. GROWTH. 



Evergreen woody plants in districts with precipitations at all seasons of the 

 year arc not endowed with continuous growth, but, like deciduous woody 

 plants, experience periodic alternations of rest and activity. The ebb and 

 flow of vegetation is very striking in the case of trees whose foliage in 

 youth is very light in colour, but assumes a dark hue in old age. In such 

 a case a tree remains for weeks, even for months, in its dark foliage ; all 

 its terminal buds are at rest. Suddenly the dark ground appears to be 

 tipped with white or bright red, the foliage-buds have flushed. More 

 frequent than simultaneous rejuvenescence of the whole crown is the 

 awakening at different times of the terminal buds of individual twigs, or 

 systems of tzvigs, from the resting to the active condition. In such cases, 

 however, the trees, regarded as a whole, give the impression of emitting 

 shoots without interruption ; yet, even if it be more concealed, there occurs 

 in them the alternation of rest and activity that is common to all vital 

 processes. 



The independence of individual systems of shoots, for instance, is very 

 strikingly exhibited by the mango-tree. Its reddish young foliage does 

 not appear at once all over the surface of its immense dark green crown, 

 but only at one or at two points, corresponding to the system of branches of 

 a longer bough, the terminal buds of which all sprout together, whilst those 

 of other boughs remain at rest. 



Usually, however, the individuality of the twigs goes still further. As 

 a typical instance of the majority of evergreen woody plants in the 

 constantly humid tropical districts we may select Amherstia nobilis, which 

 is frequently cultivated and belongs to the Caesalpiniaceae. In this, as in 

 many other trees, all the members of the system of branches are inde- 

 pendent of one another, so that twigs with resting terminal buds and others 

 with growing shoots in all stages of development are intermingled in the 

 greatest confusion. 



iii. TEMPERATE WOODY PLANTS IN THE TROPICS. 



All text-books repeat Humboldt's statement that at Cumana in Venezuela 

 the vine is in foliage and bears fruit throughout the year. I do not throw 

 any doubt on the correctness of this observation ; but, on the other hand, 



