enon. The fruit trees of the first shipment were now, however, blossoming 

 later, i. e., simultaneously with the native ones. The transition from the 

 hereditary form of growth to the new one determined by the climatic con- 

 ditions is rarely effected as rapidly as it is lost when returned to its former 

 habitat. Yet. in our vegetables, we have examples of a rapid change in 

 pecularities. In a tropical climate these keep approximately their own char- 

 acter only in the first year. Already in the second year the seeds of these 

 imported plants produce elongated, lignified specimens'. These are our cul- 

 tivated forms which are beginning to vary from the normal. No rapid 

 changes are noticeable in species growing wild, as has been shown by Hoff- 

 mann's experiments with parallel seeding of certain forms of Phaseolus 

 and Triticum in Giessen, Genoa, Montpelier, Portici and Palermo-. On 

 the other hand, Hoffmann mentions slow changes, first taking place in the 

 course of many generations. Thus Ricinus communis becomes tree-like and 

 perennial in the tropics, in the same way Reseda odorafa becomes more or 

 less persistent in New Zealand and, conversely, Bellis percnnis becomes an 

 annual in St. Petersburg. 



Among the changes in mode of growth, which are onl\- slowly com- 

 pleted, belongs the formation of the annual rings in our trees. At any rate 

 the distribution of vascular spring wood and the slightly vascular summer 

 wood within the same degree of latitude fluctuates in each year according 

 to the amount and distribution of precipitation. But in the changes 

 of the average weather, due to changes in latitude, the same dif- 

 ferences become constant and form therel)y ecolf)gical varieties. Bonnier'* 

 treats thoroughly such anatomical differences in the development of the 

 same species in northern and southern positions. He compares examples 

 of the linden, red beech, acacia and others from the region of Toulon (with 

 its 260 days of active growth) with those at Fontainebleau (growth period 

 178 days) and found that the spring wood develops better in the south, 

 hiaving more abundant, often wider ducts. In this the abundance of precipi- 

 tation in the spring in the Mediterranean district surely has a definite bear- 

 ing. The summer wood of the south, however, is richer in libriform fibres 

 and often consists only of these, while at Fontainebleau numerous ducts are 

 formed. e\en in summer. Tlie lea\es of the Toulon plants were shown to 

 be one-third to one-half thicker and pr(j\ided with more layers of palisade 

 parenchyma in comparison with the plants grown in the north. The stomata 

 are more numerous, the sclerenchyma is greater and the cuticle strength- 

 ened. The Toulon plants exhibit the character of Mediterranean flora in 

 general. 



Tlie greater intensity of the color of the blossoms, as the plants advance 

 from the plains to the mountains and from lower latitudes to northern 



1 Deutsche Gartnerzeitung, 1883, No. 17. 



- Hoffman, H., Riickblick auf meine Variaiionsversuche von 1855 bis 1880. Bot. 

 Z., 1881, p. 430. 



3 Bonnier, Cultures experimentales dans la legion mediterraneenne, etc. Cit. 

 Bot. Jahresb. 1902, II. p. 299. 



