AECD-3446(App. ) . 5 is a stimulatory effect on cells in a meristematic or plastic condition a result, there is cell enlargement or cell division or both, and the pd parts fail to differentiate into the characteristic tissues of the normal rgan on which the gall is formede The view is generally held that chemical tions of the larvae are primarily responsible for the proliferations (6) Rahn (26) mekes a novel suggestion that radiation from the larvae may sone effect. There is a close analogy between the insect gall and the develop- P adventiticua buds (7). On red currants, one of the mites produces a some- ollen bud, or a dense growth of buds which do not develop normally (1). galls are not systemic, although evidence of systemic disturbance due to a plicity of insect bites has been presented in one case (25). Even in this Ce » the effect did not extend for more than one or two internodes. an number of workers have reported tumors on plants following the applica- of indoleacetic acid (5, 8 31). When the histology of such tumors was ed by Kraus, Brown and Hamer (21) it was found that the cells of the endo- Over the vascular bundles long proliferating strands of ler tissues developed from endodermal derivatives. » and xylem proliferated greatly. & These frequently en- a sufficiently to rupture the tissues exterior to them. een much the same. RPEepee» entitious roots. Root histogens developed and later gave rise ec us Cambium, ray paren- 4 4 The responses reported for other plants x oe a ~ Some investigators claim that the galls produoed by _ > leacetic acid and other organic acids are similar to those brought about by : 4 In all cases of tumors Mase ergrowths produced by growth substances, there is a marked proliferation ‘issues which have already differentiated. The reports of adventitious shoots abbage (12), in Nicotiana hybrids (14), and in Geranium (30) indicate that The histological —# UNIVERSITY ARCHIVES UNIV. OF WASH. LIBRAR IE wT t normal recovery from growth substances is possible. S 7, $3 RR it ASE ReTE UeeeaEOREaerscis Uy rable Wo eee aa ote SE. Series wo Te AR ELECABO yet infection with the crown-gall organism (5, 22, 23)+ 2 OS he el 8 were especially responsive. 7?