125 



mentally, but finds repeated substantiation in practical experience. It is 

 namely the greater, more complete dormant period of plants. According to 

 Ihne\ trees which thrive normally in Central Europe and in Coimbra put 

 out their leaves possibly a month earlier in Coimbra and their autumnal 

 change of color occurs about a week and a half later than with us. Thus 

 their dormant period is about six weeks shorter there. The length and com- 

 pleteness of this dormant period, however, must influence greatly the rate 

 of subsequent development. It may indeed be assumed that, with the con- 

 tinuation of a temperature which does not stop the functions entirely, a 

 number of vegetative processes continue with a slow but steady consumption 

 of materials (process of oxidation) and without any compensation to the 

 plant through newly assimilated substances. Besides this, it seems that 

 many enzymes, which affect the energy of metabolism, either succeed in de- 

 veloping to the necessary amount only during a complete dormant period, 

 or are made ready for it. If no complete rest takes place it may be observed 

 especially in the two or three year old bushes and in the buds on branches 

 of woody plants. These are forced earlier and produce weaker organs 

 (smaller leaves, a greater number of sterile blossoms). 



The increased weight of the seeds in northern latitudes has already 

 been considered. There are, however, some experiments by Petermann"- 

 which prove a higher germinating pozver of Swedish seeds of clover varie- 

 ties, timothy (Phleiim prafense L.j, and of spruces and pines as compared 

 with German, French and Belgian seeds. The Swedish seeds, which 

 actually, on an average, possess a greater weight, show greater power of 

 germination, not only in the number of fertile seeds which can germinate, 

 but also in the energy with which germination takes place. These results 

 may be explained very well by a greater developmental energy in the plants, 

 due to a more complete winter rest. 



These observations have a very noteworthy practical bearing in so far as 

 they affect the culture of seeds obtained in exchange. It is not enough 

 merely to introduce seed from other regions, but it will seem necessary to 

 ask above all, what characteristics it is desired to improve in the cultivated 

 plant and in what climates these characteristics attain a higher development. 

 Taken from such localities the seed will then give the desired results. 



The cultural results, obtained by using plants of other climates, hold 

 good as a rule, however, only for a very few growth periods. Often the in- 

 fluence of the present habitat is felt in the second generation when the plants 

 of foreign importation have assumed the habits of the native varieties. 

 Fruit trees taken from Angers grew and bloomed on Malorka even at the 

 end of February, while the native ones did not blossom until a month later^. 

 A shipment made two years later from Angers showed the same phenom- 



1 Ihne, Phanolog-ische Mitteilungen. Cit. Bot. Jahresb. 1898, II, p. 409. 



- Petermann, Recherches sur les gi'aines ori^naires des hautes latitudes. 

 Extrait du t. XXVIU. des Memoires couronnes et autres Memoires publics pai- 

 I'Acad. Royale de Belgique, Bruxelles, 1877. 



3 Gartenzeitung von Wittmack, 1882, p. 374. 



