498 The Botanical Gazette. [November, 
ment of a gall, which, however, may show a marked differ- 
ence in its exterior aspect and internal structure. 
The cynips-gall may be taken as a good example. It is often 
globular and the anatomical structure shows the differentiation 
of two or more (frequently of three) concentric layers as fol- 
lows: 1. The parenchymatic outer layer with epidermis, which 
contains tannin, and may therefore be called the tannin-layer. 
The cells of this tissue are mostly arranged radially. 2. The 
protective layer, Frank’s ‘‘Schutzschicht” and Lacaze-Duthier's 
‘*couche protectrice,” which most often consists of sclereids. 
3- The inner or nutritive layer, Lacaze-Duthier’s ‘‘couche 
alimentaire,” which is composed of thin-walled parenchyma, 
the cells of which are frequently provided with large pores. 
This tissue contains an emulsion of oil, sugar and albumen; 
it is often very loose and shows large intercellular spaces. 
These layers are, however, not observable in all forms of 
galls; they are, according to the author, especially character- 
istic of the cynips-gall. 
But if we consider galls in general, the author makes the 
following statements: 1. Vegetable tissues become devel- 
oped, which enclose the animal embryos or fungus spores; OF 
else the existing tissues become utilized for the enclosure or 
covering of these embryos or spores. 2. These tissues de- 
velop a nutritive layer. 
The nutritive layer develops from its inner epidermis round- 
ish sacs or long papillose hairs, or the cells may possess only 
pores, through which the nutritive materials can pass and be- 
come utilized by the larva. It would appear that vegetable 
galls might be produced artificially with the same success aS 
has been done with the common fresh water mussel, where the 
introduction of a mustard seed developed a pearl. This does 
not seem to be the case, however, according to numerous eX- 
periments made by the author. The following. substances 
were tried on plants: formic acid, acetic acid, tincture of can- 
tharides, croton oil, mustard oil, lactic acid, potassium iodide, 
iodine, lead acetate, suet, albumen, yeast, and sugar. The 
injections were made by means of a horn pin, with which the 
author punctured the midrib of leaves or young shoots, and 
subsequently introduced the solutions through capillary glass 
tubes. He finally introduced a small piece of black must: 
seed and covered the opening with court piaster. The result 
was, however, negative in all instances. Similar experiments 
