1010 ^ 



Compound or multilocular external galls are due : — 



1. To cohesion of simple tumours, allied to the fifth group described 

 above : briar-gall. 



2. To the development of a hollowed, cellular mass. They may 

 be compared with different groups of the unilocular, being sometimes 

 hard (tumours on roots of oak) or spongy (oak-apples). 



In all the external galls, whether simple or compound, the fibro- 

 vascular bundles are placed on the outside of the protecting layers. 



Internal galls are true or false. 



True galls contain the insect in the interior of their tissues. They 

 are hypertrophies, and have their seat upon all parts of the plant, — on 

 the parenchyma, the nerves, the petioles, the cellular tissues, cortical 

 fibres, medullary rays, and the pith. 



False galls are hypertrophies, deforming the organs, and affoi'ding 

 the insects protection and nourishment. But the parasites are always 

 on the outside of the tissues of the plant. To this division belong 

 the egg-masses of aphides found on the leaves of the poplar, lime, 

 elm, &c., and the nodosities of the trunk of the apple-tree. 



The vegetable hypertrophy, in whatever form of gall it developes 

 itself, does not cause the disappearance of any of the organic ele- 

 ments : it increases their number and volume, and modifies their form. 



The cause of external galls is the deposit of a liquid venom, with 

 specific properties, — a true morbid poison, secreted by the insect, 

 which deposits it in the plant with its e^g. The form, consistence, 

 &c., of the tumours vary with the specific properties of the virus of 

 which they are the consequence. 



Internal galls, and more especially the false, appear to owe their for- 

 mation, as Reaumur has shown, to the abstraction of the liquids of the 

 plants by the suction of the Aphides, This abstraction, in augment- 

 ing the vitality of the part, deterinines, also, its hypertrophied growth. 



We could make a third general division, presenting at the same 

 time the characters of external and internal productions ; e. g., arti- 

 choke-galls. 



The paper elicited considerable discussion. — R. R. 



A Field Day of Naturalists, at Eastnor, Herefordshire. 



A Naturalists' Club having been recently formed at Malvern, the 

 Woolhope (Herefordshire) Naturalists' Club invited the newly-consti- 

 tuted body, together with the Cottesvvold (Gloucestershire) Club, to 



