EMBRYO, SEED AND CARPEL IN THE DATE. 135 



out in Green's work) taken together with the hydrolysis 

 just mentioned, indicate that the comparison of the plastic 

 tannin in the date endosperm with transitory starch is sub- 

 stantiated. Confirmatory evidence is had further in the 

 fact that fund can assimilate tannin, among other aromatic 



substances, 



24 



d a very low food 



questioned. Such tannin as is here described for the date 

 may, however, not be a food of direct availability, but may 

 be a link in a chain of metastates, or may afford energy in a 



more 



Embryo. An account of the occurrence of tannins 



em 



from 



em 



after fertilization, with the developing endosperm, is richly 

 supplied with tannin. A pronounced general reaction is ex- 



hibited by the era 



embryo measures 



mm 



mm. When full sized, the embryo measures 1.1 mm. by 2.1 



, an increase which is accomplished in a period (13 

 weeks) equal to that required to reach the smaller dimen- 

 sions. During this second period the tannin content of the 

 embrvo becomes less and less marked. Nevertheless, until a 



time 



a distinct reaction is 



discoverable, and, though it is diffuse throughout the tissues 

 of the embryo, there is evident a more marked amount of tan- 

 nin (1) beneath the epidermis of the cotyledon, (2) along the 

 vascular tracts, (3) in the plumule and the tissue beneath it, 

 and (4) in the active zone of cells between the hypocotyl and 

 radicle, which, of course, are both very short and not readily 

 distinguishable. These peculiarities of distribution are clear- 

 ly connected with the physiological function of the tannin. 

 At maturity, and during the resting condition tannin is quite 

 absent, as stated by Sachs. There are, so far as I have ob- 



« Nageli and Reinke, quoted by Pfeffer, Physiology of Plants, p. 

 492. M. T. Cook has shown recently that tannin is a poison. It is, of 

 course, obvious that different substances may be meant. 



