288 BOTANICAL GAZETTE [ocTOBER 
It is obvious that the seeds which fail to grow in the ordinary 
grain tests often do so because of seed coat characters rather than 
because of lack of vitality of the embryos. This, however, does not 
in any wise invalidate the ordinary methods of testing grains to be 
used for seeding, since seeds that are delayed a month or more in 
germination are of no value in producing the crop. On the other 
hand, when it comes to testing weed seeds, looking toward extermi- 
nation, it is highly important that these seed coat characters be taken 
into consideration. 
I am impressed by the high vitality of weed seeds. This is 
especially true of the more noxious weeds and those in which the 
seed coat secures a long delay. The high vitality is not shown alone 
by a quick response to germinative conditions. The percentage of 
germination in noxious weeds, provided real germinative conditions 
are given (the seed coat hindrance removed), is very close to 100; 
and a marked growth of the embryo generally takes place within 
two days after being subjected to germinative conditions. After 
recognizing this fact, one is led to suspect that many other cases 
of low vitality in weed seeds mentioned by Duvet and others (not 
examined in this paper) must be due to seed coat characters rather 
than to lack of vitality in the embryos. 
While this paper indicates, exactly contrary to the conclusions 
commonly held, that delayed germination is in most cases secured by 
seed coat characters, it yet recognizes that in the hawthorns delay 
is secured by embryo characters. It is probable that a number of 
other seeds will be found to belong to the same category as the haw- 
thorn. It is of great interest to know just the changes which take place — 
in the seeds of the hawthorns and finally lead to germination through 
long exposure to germinative conditions. This subject is now under 
investigation. It must be urged that, until these changes are under- 
stood, any attempt to determine the vitality of such seeds is futile. 
The methods by which seed characters that secure delayed germ! 
nation have come about naturally deserves consideration. It may 
be adaptation coming through natural selection, but an attempt to 
prove this would end in failure. This delay in many cases, however, 
is of undoubted advantage to the species. ARTHUR urges that 10 
the cocklebur the two seeds are borne in an indehiscent structure, 
