LOCATION 457 



cells containing the material to be acted upon. In other cases 

 they are formed in the same cells as the substrate. 



A few examples may be given. In Zea Mais the cells of 

 the surface of the scutellum next the endosperm have a dis- 

 tinct gland-like appearance, and here and there they dip down 

 into the deeper layers of the scutellum, giving an appearance 

 not unlike the crypts of Lieberkiihn of the intestine. These 

 secretory glands of the maize, however, have no lumina. In 

 Phoenix dactylifera the secretory organ of the seed is the 

 rounded structure situated opposite the furrow. In Nepeyithes 

 and other insectivorous plants special glands occur in appro- 

 priate places, e.g. in the lining membrane of the pitchers, or in 

 special tentacles, as in Drosera. 



The pericarp of the fruit of Rhamnus infectorius contains 

 a glucoside, xanthorhamnetin, which, on hydrolysis, breaks 

 up into glucose and rhamnetin, a yellow compound. This 

 hydrolysis is brought about in nature by an enzyme which is 

 contained in the parenchyma of the raphe of the seed. To 

 illustrate this, the following experiment may be tried : — 



An aqueous extract of the separated pericarp is made and 

 placed in a glass vessel, then into the solution is thrown the 

 raphe of a seed. A golden yellow precipitate comes down.* 

 A parallel case is furnished by the seeds of Lunaria biennis 



(p. 240). 



In other cases the enzyme and substrate are contained in 

 different cells of the same tissue, so that it is only necessary to 

 crush up the tissue, or to macerate it, in order to obtain the re- 

 action ; the bitter almond, containing emulsin and amygdalin, 

 may be given as an example. 



The enzyme-secreting cells of Zea and Phoenix have been 

 studied by Reed.f He finds that in the resting condition 

 these elements are crowded with granules of a protein nature 

 which disappear as secretion begins. At the beginning of 

 secretion, the nucleus is poor in chromatin, but this material 

 increases in amount as germination proceeds, the nucleolus 



* Ward and Dunlop : " Ann. Bot.," 1887, 1,1. 



t Reed : id., 1904, 18, 267 ; see also Huie : " Q.J.M.S.," 1897, 39, 

 387 ; 1899, 42, 203. 



