MECHANICS OF DORMANCY IN SEEDS II 3 
15 to 50 days. Maze^^ found that seeds retain their vitaHty but a 
short time even under the considerable reduction in oxygen supply 
involved in water storage. Besides injury from toxic products of 
intramolecular respiration he found leaching of stored foods very 
extensive in some cases. 
In the light of these facts the question occurs, Why is it that many 
seeds can have their germination inhibited by a sub-minimal oxygen 
supply without suffering from toxic products of partial anaerobic 
respiration? To answer this question we need a thorough study of 
the products of anaerobic and partial anaerobic respiration in cocklebur 
and other seeds of similar behavior. 
In this connection we should also remember that seeds of various 
water plants^o will withstand storage under water for years and with 
removal of coat restrictions will germinate fairly rapidly and grow 
rather extensively in total absence of oxygen. In these seeds anaerobic 
respiration apparently produces little if any poisonous products. 
Shull" has observed that seeds of a number of wild forms, including 
both water and land plants, will withstand at least years' storage 
in water. The discrepancy between these results and those of Maze 
is probably best explained by the fact that ShuU was working with the 
seeds of wild plants while Maze was dealing with cultivated species. 
A student in this field is impressed by the fact that through cultivation 
seeds have largely lost those characters that make for long dormancy 
and in general for success in the struggle under natural conditions. 
Characters we have already pointed out for various seeds of wild 
plants will largely explain the findings of ShuU. Hard coats, restricted 
swelling, partial anaerobic respiration that does not produce toxic 
materials, and perhaps finally the disposition of certain seeds to keep 
stored foods in the condensed rather than in the hydrolyzed condition, 
are all found in one seed or another showing dormancy and all reduce 
the rate of food exhaustion and tend to maintain a healthy condition 
of the embryo. 
5. Turning to the fifth general method by which dormancy in 
seeds is secured, we find a situation not met in the previous classes: 
the embryo or a part of it fails to grow when naked and supplied with 
all the external conditions necessary for germination. It must go 
through a series of changes or after-ripen before germination can 
Maze. Ann. Ins. Pasteur, 14: 350. 1900. 
" Shull. PI. World, 17: 329. 1914. 
