S. H. Taylor
Feb 1, 1949
Citations
0
Influential Citations
12
Citations
Journal
American Journal of Botany
Abstract
THE PROBLEM of cell growth and its control is of major importance in biological research today. Galls offer an excellent opportunity for study of abnormal tissue initiation and growth both because of their abundance and the comparative simplicity of the tissues involved. European botanists in the latter part of the 19th century catalogued and observed galls and gall-makers and made a few anatomical studies of galls. Relatively little research on galls has been carried on since the turn of the century. Gall studies need reinterpretation and further investigation in the light of more recent developments in the fields of anatomy, cytology, and physiology. Toward this end the present study undertakes to determine how -gall growth takes place, how normal leaf cells compare with gall cells, and if possible, the nature of the stimulus for gall formation. The gall of Nepeta hederacea was selected for study because normal leaf growth is relatively simple with only primary tissues involved except in major veins. MATERIALS AND METHODS.-Materials were collected near Roanoke, Virginia, in Charlottesville, Virginia, and at Blandy Experimental Farm near Boyce, Virginia. Seventy stem apices and over sixty galls of graduated size were fixed in formalinacetic-alcohol for 18-24 hr., or in Randolph's modification of Navas'hin for 12 hr. Galls to be tested for ribose nucleic acid were fixed in Helly's mixture (Lee, 1937) for 12 hr. and later treated with iodine alcohol. The stem apices and galls were dehydrated and cleared in ethyl alcohol and chloroform respectively, after which they were embedded in a 1 :1 paraflin-Tissuemat combination. Stem apices were sectioned at 7 and at 12 /, either longitudinally or transversely. 'Galls were cut at 7 and at 12 I, longitudinally, transversely, or paradermally. For general anatomical study most of the sectioned material was stained with safranin-fast green or safranin-anilin blue using tannic acid mordant. Photomicrographs were made in most cases from slides stained with safranin-anilin blue. Sectioned material for nuclear observations was stained by the Feulgen reaction. Tissues fixed in Helly's mixture to be tested for ribose nucleic acid were treated with ribonuclease.2 Twenty slides were placed in distilled water con-