

158 BOTANICAL GAZETTE [February 



not seem to support the theory that the insect injects some chemical into the 

 leaf which causes gall formation; (7) intumescences produced by chemical 

 sprays result from entirely different kinds of hyperplastic responses than 

 hyperplastic gall growth; (8) the investigation establishes the fact that the 

 proboscis may pass through the entire thickness of the leaf; (9) the insect 

 remains fixed, and that portion of the leaf in which the proboscis is fixed is 

 marked by lack of growth as compared with the huge outgrowths which sur- 

 round it; (10) the continuous sucking action by the insect at one fixed point 

 for fifteen days is believed to be the initial stimulus for gall development/ ' 



Another very interesting paper is by Wells, 10 who has made a study of 

 the galls of our common American hackberry. The purpose of the paper as 

 stated by the author is as follows: " (1) to present a survey of the known insect 

 and mite galls of Celtis occidentalis L. ; (2) to elucidate the history of the normal 

 gall-bearing parts of the hackberry and that of the galls; (3) to study com- 

 paratively the structures treated, pointing out any significant conclusions and 

 generalizations that may be attained in such a study.' ' The author gives 

 excellent descriptions of the external and histological character of the galls 

 and concludes the paper with the following summary: "(1) there are 17 known 

 species of zoocecidia occurring on Celtis occidentalis, belonging to 4 orders of 

 arthropods (Acarinae 1, Lepidoptera 1, Hemiptera 5, Diptera 10); all are 

 heteroplasias, that is, those forms of hyperplasias (abnormal increase in size 

 through cell proliferation) whose cells and tissues differ from the normal; all, 

 be it noted, are built up on the basis of the same germ plasm, namely, that of 

 the single species of the plant mentioned; (2) the acarinous and lepidopterous 

 galls are kataplasmas of those forms of heteroplasias whose cells and tissues 

 do not vary widely from the normal; each shows specific and characteristic 

 inhibition of differentiation; (3) the hemipterous and dipterous galls are proso- 

 plasmas of those forms of heteroplasias whose cells and particularly whose 

 tissue forms differ fundamentally from those of the normal parts; (4) in the 

 prosoplasmas the types of cells found are closely comparable to those of the 

 normal plant parts, but the tissue forms discovered are fundamentally new; 

 no analogous structure forms are to be found in the tissues of the normal plant 

 or its allies; (5) in the dipterous prosoplasmas, since the gall's specific tissue 

 form characters are related to the species of insect, we have the unique case 

 of the 'overlapping' of the hereditary constitution of an animal on that of the 

 plant in the sense that factors associated with the insect determine the form 

 character locally, rather than those normally associated with the plant's germ 

 plasm; these latter plant factors suffer suppression; (6) it is suggested that in 

 the field of zoocecidiology we probably have a unique place, heretofore unrecog- 

 nized, to attack the problem pertaining to the mechanism used in the expression 

 of hereditary characters." The paper is well illustrated. — Mel T. Cook. 



10 Wells, Bertram W., The comparative morphology of the zoocecidia of Celtis 

 occidentalis. Ohio Jour. Sci. 16:249-290. 1916. 



