Some Problems in Cecidology

Abstract

It is very doubtful if any phase of biology has been neglected more than that very conspicuous and extremely puzzling branch known as cecidology. This subject in its broadest sense includes all forms of abnormal plant growth regardless of cause. It must include, therefore, not only the hypertrophies, but also the witches brooms. It must include the abnormal growths caused by flowering plants, fungi, bacteria, insects, nematodes, and chemical and mechanical injuries. It must also include that great number of abnormal growths from unexplained causes which are included under the general term of teratology. Unfortunately, many of the botanists have interpreted the subject to include only those cecidia which are the result of insect injuries, and have attempted to relegate the entire subject to the entomologists, although they have not hesitated to study the cecidia caused by nematodes and bacteria, which might just as reasonably be forced upon the zoologist and bacteriologist. The fact that the mycologists have usually been interested in the fungi and not in the host plant, explains why so much interesting material has been thrown aside with the single comment, bugs. But with the development of plant pathology, a branch of botany which is necessarily interested in the pathological condition of the host, there is no longer any excuse for not giving a reasonable consideration to all phases of cecidology. It is the purpose of this paper to call attention to some of the problems involved in cecidology, and to their bearing on other phases of biology, more especially botany. Cecidology is as old as the science of biology, and cecidia are referred to in some of the earliest biological literature. That cecidia were the subject of speculation, if not of study, is evidenced in the writings of REDI,' who, like other vitalists of his period, believed plants were endowed with souls and that the soul of the plant controlled the formation