[24 THE AMERICAN I'.OTANIST 



in a night as would a single lamp. We must remember, loo, 

 as regards the general effect of plants on the health, that 

 invalids arc often sent to the country to recuperate where there 

 is little else but plants. When it comes to flowers in the sick- 

 room, however, that it quite another story. Flowers often give 

 <ilT odors that arc harmful even to persons in good health but 

 this is not a result of breathing or of the formation of 

 plant food. 



THE EVOLUTION OF HERBS 



r I '! I E origin of our plants has always been an attractive sub- 

 ject for speculation by the evolutionist. As data accum- 

 late, it becomes increasingly evident that the first plants were 

 evergreen, perennial, and, so far as land plants are concerned. 

 tree-like in form. Herbs seem to have been a later response 

 of vegetation to increasing cold and drouth which they en- 

 countered in less favorable parts of the earth. Such forms, 

 however, enabled vegetation to exist in regions where other 

 forms could not grow. In practically every instance, where 

 plant families contain both herbs and trees, the woody forms 

 have been shown to be earlier and more primitive. The cycads, 

 the pines, spruces and other cone-bearers from which modern 

 flowering plants appear to have descended, arc all woody 

 plants and appear always to have been so. Even the simpler 

 flowering plants, such as the catkin-bearing Amentiferae and 

 the relatives of the butter-cup family are nearly all tree-like in 

 form. If the inference is correct that herbs are due to cold 

 and drouth, we would naturally expect the plants of cold 

 regions to be largely herbs, and this turns out to be the case. 

 As regards the effect of this herbaceous vegetation on the de- 

 velopment of modern forms of life on our planet, the follow- 

 ing from 'The Evolution of Herbs," by Dr. Edmund W. 

 Sunn >tt in Science is pertinent. 



