DELAYED GERMINATION. 
BY L. H. PAMMEL AND CHARLOTTE M. KING. 
In 1901 there was begun^ a study of the germination of weed seeds 
under different conditions. It was observed that a large number of the 
weed seeds did not germinate freely in the fall. 
In 1902 an experiment was performed with both mature and imma- 
ture seeds. Plantings of these seeds w^ere made in both fall and spring ; 
the spring planting included both seeds which had been frozen and 
seeds which had not been frozen. It was found that seeds of different 
species showed great difference in germination. In general the results 
of 1902 and 1903 indicate that stratification in sand and freezing is 
favorable to germination ; thus, in the Milkweed {Asclepias syriaca) , 
there was no germination upon stratification but afterwards 12 per 
cent; Western Ragweed (Aml^rosia psilostachyo.) , none before and 18 
per cent afterward; Lamb’s quarter {Chenopoditim album) none before 
and 88 per cent after stratification; Cocklebur {XantJiiiim canadense) 
none before and 25 per cent afterward. 
Subsequently Mr. LI. S. FawcetP made a study of 52 different samples 
of mature weed seeds representing 52 different species. The samples 
were collected in September, October and November of 1904. The seeds 
were threshed out and placed in paper envelopes. Fifty seeds of each 
sample were placed in sand in boxes in a greenhouse and kept under 
conditions as nearly uniform as possible. The tests were repeated each 
month from November until May and all boxes of the previous months 
left. They were kept moist during the winter. In addition a large 
numher of weed samples was placed out of doors to expose them to 
the freezing and thawing, the seeds being placed in sacks in a wooden 
box covered with a thin layer of sand; the box was sunk in the ground 
not more than a foot below the surface and left there all winter. The 
general effect of the thawing and freezing was to increase the percentage 
^Pammel, L. H. Proc. Soc. Prom, Agrl. Sci. 24:89. 
‘The Vitality of Weed Seeds under Different Conditions of Treatment and a 
Study of the Dormant Periods. Proc. la. Acad. Sci. 15:25. 
