THE PLANT AND ITS RELATIONS ,3 



lime, knmquat, grape-fruit. Other families contain only one or two agricultural plants of commanding 

 importance ; as cotton, of the Malvaeem or mallow family ; flax, of the Linacece or flax family ; buck- 

 wheat, of the Polygonaeem or knotweed family ; beets and mangels, of the Chenopodiacex or pigweed 

 family ; sweet-potato, of the Convolvulaeew or morning-glory family. 



The number of distinct species of flowering plants now described is about 125,000. What this vast 

 number has so far contributed to the food requirements of man has been made the subject of an inquiry 

 by Sturtevant (Agricultural Science, iii, p. 174). Basing his list on Bentham and Hooker's "General Plan- 

 tarum" (1862-1883), in which about 110,000 species of flowering plants are recognized, in some 200 fam- 

 ilies and 8,349 genera, he arrives at the following figures : 4,233 species, belonging to 170 families and 

 1,353 genera, are known to have furnished food for man either habitually or during famine periods ; 

 1,070 species, belonging to 92 families and 401 genera, are or have been cultivated for human food. Among 



Fig. 3. A mushroom, one of the non-vascular flowerless plants. It is saprophytic. 



flowerless plants 431 species have been recorded as edible, but only 5 or 6 are cultivated. In other words, 

 about 3J per cent of the known species of flowering plants furnish parts which can be eaten, and nearly 

 1 per cent are or have been cultivated for human food. About 300 species are cultivated to an impor- 

 tant or commercial extent. 



De Candolle, in "Origin of Cultivated Plants," discusses the origins of 247 species which are 

 " cultivated on a large scale by agriculturists, or in kitchen-gardens and orchards." These belong to 51 

 families. They may be tabulated as follows : 



Native to the Old World Native to the New World 



A. Cultivated for more than 4,000 years . 44 D. Very anciently cultivated 5 



B. Cultivated more than 2,000 years ... 47 B. Cultivated when America was discovered, but 



C. Culture less than 2,000 years 61 less ancient 24 



Doubtful 47 F. Cultivated only since discovery of America . . 6 



Doubtful 10 



199 



45 



Of A, 50 per cent are annuals, 5 per cent biennials, 4 per cent herbaceous perennials, 41 per eent 

 ligneous perennials. 



