CHAPTER IV 



ACCLIMATISATION 



A.CCLIMATISATION may be described as the accustoming of 

 plants to new conditions and climates till they are not only 

 capable of growing there, but also of reproducing themselves 

 freely. Thus, though the cherry and apple will grow readily 

 enough in the hills of Ceylon, they are not really acclimatised, 

 for they do not produce fertile seed, and if left to themselves 

 would inevitably die out. Lantana, on the other hand, is com- 

 pletely acclimatised, and seeds freely. 



As practised by man, acclimatisation is chiefly modern, but 

 in nature it has been going on for ages. Hers is much more 

 gradual, but there is no nursing of a delicate plant till it can 

 survive and reproduce; if in any way unsuitable to the altered 

 conditions, it will die out. Man used to try to make enormous 

 changes, as from Europe to the Tropics, but has slowly learnt 

 that this is usually impracticable, and has even begun gradual 

 acclimatisation, as for example in the way in which he has 

 treated Liberian coffee in Java, taking the seed of successive 

 generations a few score yards higher up each time, till he has 

 persuaded the tree to do well at a much higher elevation than 

 that to which it is naturally suited. 



In the Ceylon Botanic Gardens we were very anxious to 

 acclimatise the beautiful Cyperus Papyrus; so long as we tried 

 seed from Europe we failed, but seed from Saharanpur in India 

 succeeded at once. Sometimes the difficulty is M'ith change of 

 climate in regard to periodicity, as when one tries to acclimatise 

 plants of the southern hemisphere in Europe. Sometimes the 

 plant requires a mycorhiza (or fimgus in association with the 

 roots) for its successful growth, and it may not be possible to 

 persuade this to grow, as with heather in Ceylon, which has 

 never succeeded there. But it would lead too far to discuss all 

 the many and complex i^hcnonienu uf neelimatisiilloii !ifi prac- 

 tised by man, and we must return to that carried on by nature, 

 which almost never attempts to make great changes at once, 

 except when, for example, the Gulf Stream carries to Europe 

 seeds which refuse to grow there except in hothouses. 



As a rule, nature's acclimatisation is simply to the slightly 



