8 o 
Vol. XXIII, No. a 
Journal of Agricultural Research 
A great deal of work has been done by others on the after-ripening 
of seeds in general and more with the cereals than with any other class 
of seeds on account of their economic importance. Much of this work 
with the cereals by English and German investigators has been related 
to the adaptation of fresh grain for use in the brewing industry, although 
relations to agricultural practice and breeding have not been entirely 
neglected. Many and various hypotheses have been put forward to 
explain the process of after-ripening, but some of these lack convincing 
experimental evidence and none is of universal application. 
RESUETS OF THE INVESTIGATION 
EFFECT OF ARTIFICIAL DRY HEATING 
Duchartre (rj>), 3 working with spring rye, wheat, and barley, was one 
of the first to call attention to the beneficial effect of artificial drying on 
the germination of seeds. He found that cereal seeds were capable of 
germination when they were still far from mature and their endosperms 
were just leaving the milk stage; that very young seeds germinated more 
slowly, but with as high a total percentage as the fully ripened grain; 
that artificial drying so affected these very young seeds that they ger¬ 
minated about as rapidly as the mature grain; and that such artificially 
dried young grain was satisfactory for seeding purposes. 
Since Duchartre’s publication, the New York (Geneva) Agriculture 
% Experiment Station (40), Hotter {24), Hoffman (22, 23), Hiltner (21), 
Atterberg (6), Kiessling ( 28 ), and Stapledon and Adams (39) are among 
those who have published results showing favorable effects upon ger¬ 
mination from drying not after-ripened cereals and maize. Zade (47) found 
only slight advantage from artificial drying of wild oats when fresh, but 
when the dormant seeds which had been in moist sand for months were 
removed from the sand, dried, and remoistened a very large percentage 
germinated promptly. 
Recently Kondo (30) has shown beneficial effects from drying not after- 
ripened rice. He considers this to be due to an increase in the oxygen 
supply made possible by a change in the oats. This explanation seems 
to be applicable to Zade’s favorable results with wild oats, since Atwood 
(7) has shown that oxygen is the limiting factor in the germination of 
these seeds. 
In nearly all the published work on artificial drying to hasten the after¬ 
ripening and germination of cereals the drying has been done by means of 
heating, and the results are therefore complicated by a possible effect of 
the heating per se. In fact Kiessling, in the article already cited, at¬ 
tempted to show that the beneficial effects he secured w r ere really tem¬ 
perature effects and not effects of fluctuations in moisture content at 
all. However, Hiltner (. 21) and others have shown an accelerating effect 
upon after-ripening as a result of drying in vacuo or over sulphuric acid. 
The writer, in conjunction with Dr. William Crocker in work as yet un¬ 
published, accelerated after-ripening of Johnson grass seed by drying over 
lime or over sulphuric acid, but the effect developed much more slowly 
and less completely here than when the seeds were heated in a drying 
oven. Apparently in this case both heating and drying are beneficial 
and the result seems to be related to the subsequent w r ater intake of the 
embryo. 
3 P,eferen<e is made by number (italic) to “ Literature cited,' p. 97-100. 
