460 ORIGIN OF CULTIVATED PLANTS. 



2. The characters which have most varied in cultiva- 

 tion are, beginning with the most variable : a. The size, 

 form, and colour of the fleshy parts, whatever organ they 

 belong to (root, bulb, tubercle, fruit, or seed), and the 

 abundance of fecula, sugar, and other substances which 

 are contained in these parts ; 6. The number of seeds, 

 which is often in inverse ratio to the development of the 

 fleshy parts of the plant ; c. The form, size, or pubes- 

 cence of the floral organs which persist round the fruits 

 or seeds ; d. The rapidity of the phenomena of vegeta- 

 tion whence often results the quality of ligneous or 

 herbaceous plants, and of perennial, biennial, or annual. 



The stems, leaves, and flowers vary little in plants 

 cultivated for those organs. The last formations of 

 -each yearly or biennial growth vary most; in other 

 terms, the results of vegetation vary more than the 

 organs which cause vegetation. 



3. I have not observed the slightest indication of an 

 adaptation to cold. When the cultivation of a species 

 advances towards the north (maize, flax, tobacco, etc.), it 

 is explained by the production of early varieties, which 

 can ripen before the cold season, or by the custom of 

 cultivating in the north, in summer, the species which in 

 the south are sown in winter. The study of the northern 

 limits of wild species had formerly led me to the same 

 conclusion, for they have not changed within historic 

 times although the seeds are carried frequently and 

 continually to the north of each limit. Periods of more 

 than four or five thousand years, or changements of form 

 -and duration, are needed apparently to produce a modifi- 

 cation in a plant which will allow it to support a greater 

 degree of cold. 



4. The classification of varieties made by agricul- 

 turists and gardeners are generally based on those 

 characters which vary most (form, size, colour, taste of 

 the fleshy parts, beard in the ears of com, etc.). Botanists 

 are mistaken when they follow this example ; they 

 should consult those more fixed characters of the organs 

 for the sake of which the species are not cultivated. 



5. A non- cultivated species being a group of more or 



