USEFUL AND HARMFUL PLANTS 303 



tain animals may be fatal to themselves. Since, however, 

 some of these plant poisons are among the most valuable of 

 medicines, it is plain that no dividing line exists between 

 harmful and useful plants. Judged in its relation to our 

 welfare the same plant may be either useful or harmful 

 according to what we do with it. Obviously, the more we 

 know about their properties the less likely are we to suffer 

 harm from plants, and the more likely are we to benefit by 

 them. 



The student should understand clearly that in this book the 

 aim is only to introduce beginners to the study of plants. 

 Our purpose is merely to lay a good foundation for future 

 studies which shall further advance general culture. There 

 has been no intention of giving here a complete outline of 

 economic botany. Accordinglj-, a great many plants of high 

 economic importance have not been mentioned; and some 

 of the chief uses of plants, and some of the most serious ways 

 of their working harm, have been passed over ^vith bare 

 mention, or have been ignored. Thus, in regard to the food 

 of domestic animals but little has been said of the fod- 

 der raised for them, and nothing at all of pasture plants 

 upon which some of the principal industries of the world 

 depend. The many plants which afford bees the material 

 for making honey and wax, and those which serve as food for 

 silkworms or other irusects of economic value have also been 

 neglected. So also have we omitted reference to the plants 

 which do great service in binding shifting sands that but 

 for these sand-binders would devastate extensive areas: to 

 those plants similarly used to prevent the washing away of 

 soils; to trees set out as wind-breaks for protecting tender 

 vegetation, as drainers of swamp land, or for shade and 

 beauty; and to the innumerable flowers and foliage plants 

 cultivated or collected for ornament. Likewise, among 

 harmful plants neither weeds nor destructive parasites have 

 been included. 



Not only has our study neglected these groups of plants 

 which especially affect the welfare of mankind l5ut it has 

 been forced to leave out of account some most extensive in- 

 fluences which vitally concern animals in general. For ex- 



