Septembee 1, 1916] 



SCIENCE 



297 



"With these various advantages it is not sur- 

 prising that the herbaceous habit to-day 

 characterizes not only great numbers of the 

 commonest and most dominant native plant 

 species in all parts of the world but also 

 that huge array of hardy and ubiquitous 

 plants which we know as weeds. 



This radical change in the growth habit 

 of many plants from a woody to an her- 

 baceous type which has taken place for the 

 most part since the beginning of Tertiary 

 time cannot have failed to exert an im- 

 portant influence on animal life. It may 

 well be connected with the rapid evolution 

 of mammals which we know to have oc- 

 curred after the early Tertiary. To quote 

 from Chamberlin and Salisbury: 



The earliest Eocene mammals were much more 

 primitive and obscurely differentiated than even 

 those of the middle Eocene, and this rapid back- 

 ward convergence seems to point to some set of 

 conditions which caused an exceptionally rapid 

 development of the great class at this stage, what- 

 ever their previous history had been. The coming 

 into a new domain of rich and varied conditions, 

 whether by immigration or indigenous develop- 

 ment, may be safely included among those condi- 

 tions. 



Is it not reasonable to suppose that the 

 appearance of a great body of herbaceous 

 vegetation just at this time was one of 

 these conditions? This would affect di- 

 rectly the development of all herbivorous 

 types and indirectly of many others. In 

 the evolution of the tooth of the herbivora, 

 indeed, we can trace the change from a 

 sharply cusped type, suitable for chewing 

 tough leaves and twigs, to the modern flat 

 condition which is capable of dealing only 

 with the softer herbaceous tissues. 



The development of herbs was also ap- 

 parently of some importance in the evolu- 

 tion of bird life, for the appearance of an 

 immense new food supply produced by this 

 terrestrial, seed-bearing vegetation, must 

 certainly have led to the much greater 

 abundance of such ground-loving types as 



the finches and others, and may well have 

 been responsible for their origin. So 

 closely are plants and insects related, too, 

 that a radical change in the one can not 

 have been without effect on the other. 



Far more important, however, is the part 

 which the herb has played in the develop- 

 ment of human civilization. Primitive 

 man seems to have been mainly arboreal 

 in his habits, or at least primarily a forest 

 dweller, and the wood, bark and fruit of 

 trees and shrubs were of supreme impor- 

 tance to him as sources of shelter, fuel, im- 

 plements, clothing and food. One of his 

 first steps from this barbarism toward 

 civilization was to enter the open and begin 

 the practise of agriculture. Those plants 

 which most commended themselves to the 

 earliest tillers of the soil were probably not 

 the slow-growing trees and shrubs but 

 rather the herbs, since the rapidity with 

 which they grow and reach maturity makes 

 possible their culture even among such rov- 

 ing tribes as were our North American 

 Indians. Only as man acquired a settled 

 place of abode and a more permanent form 

 of society could he begin the culture of 

 woody plants in orchard and vineyard ; and 

 it is only in very recent times that agri- 

 culture has extended beyond these fruit- 

 bearing trees and shrubs and, in the form 

 of forestry, has begun to treat timber trees 

 themselves as a crop to be cultivated. 



The marked superiority of the herb in 

 ease of agricultural manipulation, together 

 with the wide variety of uses of root, stem, 

 leaf and fruit, have given it an increasingly 

 high place in man's favor. To be sure, 

 trees and shrubs provide us with timber, 

 fuel, paper, rubber, fruits, nuts, coffee, tea, 

 cocoa, vineyard products, turpentine and 

 many drugs and items of lesser conse- 

 quence. Among herbaceous products, how- 

 ever, are found all the cereals and vege- 

 tables, together with sugar, tobacco, most 



