SOME PROBLEMS IN CECIDOLOGY 
Mei ¥, -Coox 
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 flower- 
ing 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 bac- 
teria, 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 interest- 
ing 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 con- 
dition of the host, there is no longer any excuse for not giving 4 
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 
* REDI was born in 1626. 
Botanical Gazette, vol. 52] [386 
