Hayfever plants

Preface: The study of hayfever falls into two fiels--the clinical and the botanical--each so broad of scope and widely differing in character that for one to excel in one is almost to preclude the possibility of excelling in the other. The past twenty-five years--approximately the time since pollen has been generally recognized as the cause of hayfever--has seen the accomplishment of much excellent work in both fields, but that of the former greatly exceeds that of the latter, and the facts of the latter field still remain scattered and so mingled with fancies that one who is not a trained botanist could scarcely be expected to separate them. This book is intended, therefore, to interpret the botanical facts of hayfever in terms of their clinical significance. Here are described all of the plants known to cause hayfever, most of those reasonably suspected of doing so, and many which have been mentioned in heayfever literature, possibly wrongly.^ In the plant descriptions I have not attempted to define the species beyond pointing out a few of the salient features which may readily be used and most easily retained in memory. The plants are presented in the sequence of Engler and Pran