A BIOLOGICAL AND SYSTEMATIC STUDY OF 
PHILIPPINE PLANT GALLS? 
By LEopoLtpo B. UICHANCO 
(From the College of Agriculture, University of the Philippines, Los Banos) 
FIFTEEN PLATES 
INTRODUCTION 
Galls are abnormal growths on the stems, leaves, roots, or 
other parts of plants, caused by the action of insects, arachnids, or 
fungi, or by unknown agencies. Just how these peculiar struc- 
tural developments are brought about is still open to discussion 
and speculation, experimental proofs being, up to the present, 
too deficient to warrant our drawing any definite conclusion. 
These malformations have been ascribed to various causes, the 
more commonly accepted, in the absence of more reasonable, ex- 
planations being the following:* 1, a severe mechanical injury 
to certain parts of the plant; 2, a continuous mechanical irrita- 
tion; 3, secretion of chemical stimulus by the causal animal or 
fungus. One, or a combination of two or all, of these causes may 
give rise to the production of galls. In the formation of zodce- 
cidia, the third factor—that is, the action of the virus secreted 
at the time of oviposition or during the development of the para- 
site—is probably the most important, the first two being of 
minor or absolutely no use whatever. This fact was shown by 
Molliard in connection with his experiments on Aulax papaveris 
Perris, a cynipid gall maker on the pistil of Papaver rhoeas 
Pall. From time to time he removed a small quantity of the 
virus secreted by the developing Awlax larva, and injected the 
fluid into the growing pistils of Papaver. This artificial treat- 
ment resulted in the formation of galls which resembled in all 
respects those formed in the presence of the larva itself. He 
was thus enabled to draw the conclusion that the virus alone, 
without the influence of mechanical irritation from the presence 
of the animal within, is sufficient to produce the characteristic 
Papaver gall. The importance of chemical stimuli, as related 
to gall formation, was recognized as early as 1686 by Malpighi, 
‘Thesis presented in partial fulfillment of the requirements for the 
degree of Master of Science, University of the Philippines, 1918. 
* Cook, M. T., Insect Galls of Indiana. Dept. Geol. and Nat. Resources, 
Indiana, 29th Ann. Rep. (1904) 801. 
*Compt. Rend. Acad. Sci. 165 (1917) 160. 
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