SUMMAKY. 19 



hard seed. No. 68 includes onl}- the hard seed selected from the 

 Oregon clover by soaking- in water for 18 and then for 20 hours a 

 portion of the original bulk sample, using only the remaining hard 

 seed. 



These results, while unsatisfactory, show clearly that it is the hard 

 seeds in the clovers which remain over in the soil for some considerable 

 time. The alsike clover, No. 50, behaved practically the same as the 

 sample of red clover first mentioned. The Lespedeza, or bush clov^er. 

 No. 43, gave results very similar to the white clover. The alfalfa, No. 

 59, gave a germination of only 2, 9, and 9 per cent, respectivel}-, for 

 the three different depths. But in all cases a few fresh sprouts were 

 present when the seeds were taken up, showing that the seeds were 

 germinating and afterwards decaying. 



SEEDS OF CULTIVATED VERSUS WILD PLANTS. 



A number of interesting cases showing the greater hardiness of the 

 seeds of wild plants over those of like or closely related cultivated 

 forms were recorded. In Ilelianthiis ammus (Nos. 6 and 97) the seeds 

 from the cultivated plant — our common sunflower of the garden — all 

 deca3'ed, while the seeds of the wild sunflower retained their vitalit}" and 

 germinated 43.5, 64, and 66.5 per cent, respectively, for the three dif- 

 ferent depths. Similarh' with Lactuca sativa and Lactuca scariola^ Nos. 

 5 and 98, respectivel}^, the common garden lettuce seed had all decayed, 

 while the seed of the prickly lettuce, possibly the parent of our cos 

 varieties, germinated 63.5, 69, and 69.5 per cent, respectively, for the 

 three different depths. Another striking example is in Avena sativa^ 

 No. 1, and Avena fatua, No. 71, the latter germinating 9, 8, and 18 

 per cent, respectively, for the three different depths, besides showing- 

 many fresh sprouts in the two shallower depths at the time the seeds 

 were taken up. 



Furthermore, it is not uncommon to find wide variations in different 

 species of the same genus, even where all forms are wild, e. g., Elymus, 

 Chaetochloa, Chenopodium, Cuscuta, Plantago, etc. But in the cases 

 above mentioned of the cultiv^ated and the closel}' related wild forms 

 the ability of the seeds to withstand such treatment as being buried in 

 the soil has l)een lost by long cultivation of the plants and the careful 

 preservation of the seeds under artificial conditions or storage, while 

 seeds from the wild forms can survive when buried in the soil, for it 

 is the plants from just such seeds that have survived. 



SUMMARY. 



The length of time that seeds will retain their vitality when buried 

 in the soil is of much importance in the extermination of weeds. 



The seeds of many of our pernicious weeds can be destroyed bj^ 

 deep plowing, if the soil is left undisturbed for some time. 



