132 



MISSOURI BOTANICAL GARDEN. 



distribution of oil in small droplets throughout the endo- 

 sperm, but whether there is any causal relation to be traced 



is not to be decided off-hand. 



Very soon the thickening of the cell walls, 





Stage III. 



to form reserve cellulose, begins, (f. 26 a). Concomitantly, 

 there is a reappearance of tannin, so that, in material two 

 weeks older, (3 months old) there is tannin throughout 21 the 

 endosperm in large amount (f. 27). The amount is how- 

 ever much greater in the central portion, namely in those 

 cells, strictly speaking, which are undergoing secondary 

 thickening of the cell walls, looking toward the definitive 

 condition of the seed. The reaction at this time is very pro- 

 nounced, and the tannin-bearing portion of the endosperm 



forms the most conspicuous feature of the seed macroscopi- 

 cally (f. 27). 



As I had some doubt of the facts here presented, another lot 

 of material was obtained for me by Professor R. II. Forbes, 

 and treated by Dr. A. E. Vinson with ethyl nitrite. The 

 material, Deglet Noor, included material pollinated March 

 9, and fixed June 9, 1910. Upon examining this, the w T hole 

 of the endosperm and the embryo were perfectly white, a 

 quite unexpected result. The area (shown by stippling in f. 

 28) which should have been deeply stained, w r as a more 

 opaque white than the surrounding zone. But upon the ad- 

 dition of ferric chlorid, a prompt reaction followed, in quite 

 the expected manner. Upon prolonged treatment with very 

 dilute ferric chloride, the central part of the endosperm was 

 stained dense blue-black, with the outer zone obviouslv less 

 so. Re-exposure to vapor of nitrous ether produced the 

 reaction also, fropi which we may infer that the period of 

 original exposure was insufficiently prolonged. 



During another two weeks the seed grows rapidly, attain- 

 ing a transverse diameter of 7 mm. (f. 29), and the tannin 

 tissue has extended toward the periphery, but is less pro- 

 nounced in its response to reagents. After this, the density 

 of the reaction is quickly reduced, but extends quite to the 



21 See also p. 134. 



