354 SCIENCE PROGRESS. 



bundles are its chief seat, certain cells of the pericycle also 

 probably containing it. In the almond emulsin is localised 

 chiefly in the pericycle of the cotyledonary bundles. 



A curious distribution of a similar ferment, rhamnase, was 

 ascertained by Marshall Ward (10). It occurs in the seeds 

 of Rhamnus infectorius, and is confined to the raphe of the 

 seed. In this, as in the preceding cases, the glucoside and 

 the ferment are not found in the same cells. 



In reviewing these cases, in which apparently rudimen- 

 tary glandular tissue is being differentiated, we see a tendency 

 to aggregate the secreting cells together. Indeed, in some 

 of the cases quoted, the tissue is produced by the continued 

 division of cells originating from a single primitive one, as 

 in the fruit of Capparidaceae and the cortex of the stem of 

 Tropseolum. A more fully differentiated structure is seen 

 in the scutellum of certain of the grasses, and the absorbing 

 haustorium of the cotyledon of the palms, which remains 

 embedded in the endosperm while germination is proceed- 

 ing. The scutellum of the grasses is covered by a delicate 

 epithelium (4), one cell thick, which is specially adapted for 

 secretion, and which puts out two enzymes into the endo- 

 sperm to work upon the cell walls and the starch grains 

 respectively. The histological changes which these cells 

 show as germination progresses, and their activity varies, 

 strikingly recall the behaviour of the animal gland cell. The 

 epithelium of the Palm haustorium has not been proved to 

 excrete enzymes, but its appearance during germination is 

 very similar to that of the scutellum, and its growth is 

 attended by a corrosion or eating away of the tissue of the 

 endosperm which is very much like that observed more easily 

 in the grasses. 



Finally we have the well-differentiated secreting glands 

 (3) of Dionsea (18) and Drosera, where we find tissue 

 specially set apart for the production of peptic enzymes, 

 intended to work upon substances exterior altogether to the 

 plant's body. 



These recall the animal enzymes not only in the mode of 

 their secretion and the position of the materials they digest, 

 but also in the fact that the enzyme is accompanied by an 



