396 



The J 



ournal o 



f Hereditv 



greatest importance, and such a house 

 would allow utilization of the full sup- 

 ply. The results of (iarner and Allard- 

 suggest, too, that artificial lighting 

 nia>' be used to sup|)lenient the natural 

 supply, and to obtain tin- optimum 

 relation between periods of light and 

 dark. 



The details are for the future. For 

 the jiresent it seems enough to point 

 out the achantages of speeding up the 

 [irogress 1)\" growing two crojis a year, 

 and the desirabilit\' of deternu'ning the 

 best practice in greenhouse corn culture 

 as well as the possibilities and limita- 

 tions of such a metliod in corn breeding. 



WAXY ENDOSPERM IN COIX AND 



SORGHUM 



J. H. Ki;mi'T()N" 

 Bureau PUmt Industry, United Stales Department of Agriculture 



I\ 1 UK endospcriu of mai/e seeds, 

 a layer of compact starch cells, 

 \ariable in thickness, encloses the 

 loose or soft starch cells that occupy 

 the center of the seed adjacent to the 

 embryo. This layer of compact or 

 hard starch cells is found in three 

 VMsibly different, genetically distinct 

 types, commonly known as horny, 

 sweet, and waxy. Kach of these types 

 is distingin'shed easily from the others 

 and from the soft type or central starch. 

 The horny type is coextensive with 

 maize and is the common form of 

 endos[)erm, not only in maize but in 

 most grasses. The sweet and wax\' 

 types have been reported onl\' in maize 

 and are restricted in distribution — the 

 former in the Americas, and the latter 

 iri Asia. .Sweet endosperm is dis- 

 tinguished frf)m the conunon, horny 

 form, chielly in the wrinkling of the 

 seed caused by the drying of imi)erfect 

 starch cells. In the' smaller seeded 

 grasses, this characteristic wrinkling 

 nn'glii be overlooked easily, or be 

 atlribiilL-d to inuu.iturity or imperfect 

 fertilization. However, crosses be- 

 tween maize with sweet endosperm and 

 Kuchlaena, the nearest .American wild 

 relative, have given onl\- hornv- seeds in 

 the first generation, indicating that the 

 sweet type of endosperm is not common 

 in Kuchlaena. 



Waxy endosperm differs from the 

 horny in texture and in being opaque 



instead of translucent. It was found 

 first in maize from China and later in 

 maize from Burma and the Philippines. 

 Maize varieties from other parts of the 

 world ha\'e been .scrutinized carefully 

 for this type of endosperm, but thus far 

 it has been found only in the three 

 widely separated regions of Eastern 

 Asia. The common occurrence of waxy 

 endosperm in the Shan states of upper 

 Burma with an extensive vocabulary 

 of native maize names has led Collins to 

 the conclusion that this t>'pe of endo- 

 sperm originated in Burma and was 

 distributed from there to China and 

 thence to the Philippines.' 



A waxy type of endosperm has been 

 found now in several varieties of 

 Coix (Job's tears) and also in one 

 variety of sorghum. In appearance 

 this type of endosperm in Coix is 

 entirely similar to the waxy endosperm 

 of maize, and presents the same sharp 

 contrast with the horny endosperm 

 as well as with the loose, or floury 

 portion of the kernels. It may be 

 expected that in Coix as in maize the 

 wax\' endosperm will beha\e as a 

 definitely, alternative character, reces- 

 sive to the horn>- form. hVom the 

 standi»)int of the origin of wax>- eiido- 

 spenu in maize it seems suggestive that 

 waxy endosperm in Coix is foimd in the 

 same isolated regions in Kastern Asia, 

 and as with maize, Burma seems to be 

 the most important center. 



Hiarncr, \V. W., and Allanl, H. A. Kffcct of the relative length of dav and night and other 

 v-'V'Pri* "■ ^'n^Tonment on the growth and reproduction in plants. In [oiirn. Agr. Res., v. 



XV III, no. II, pp. .S.S.?. 606. V)U). 



Science, \.S., \'.)!. I. II 770 I.^.^.^ pp. 



... ',S"!''!'^' *'• '^- ^^-'xy maize from iippir Hiirma. 

 4H-5I. July 16, 1920. 



