158 T H E PLANT WORLD 



THE VIABILITY OF SEEDS. 



Some interesting observations have been made recently at 

 the Arizona Experiment Station concerning the viability of 

 seeds of various economic plants after continuous prolonged 

 submergence. These experiments were suggested by condi- 

 tions which obtain in the Colorado River Valley in South- 

 western Arizona, which, as is well known, is subject to an 

 annual rise in May and June from the melting of snows in 

 the mountains near its source. By virtue of this it overflows 

 its banks, covering its flood plain to a ciepth of one to several 

 feet with water, very much like the historic Nile of Egypt. 

 There being practically no rainfall in this section of Arizona 

 and adjacent Mexico during the spring and summer months, 

 certain annual crops that are grown by other means than 

 systematic irrigation are sown on these flood plains before 

 the season of high water begins. With the clearing away of 

 the flood the seedlings appear trhough the soft, sedimentary 

 mud which is rich in nitrogen and mature a crop before the 

 land becomes too dry for favorable plant growth. 



In the experiments noted the seeds were sown in soil 

 in the usual manner and flooded to a depth of twelve inches 

 for a period of thirty-eight days, which is about the period 

 cf av^erage submergence over the lower flood plain of the 

 Colorado River. With this treatment the percentage of 

 germination of normal seeds obtained were as follows: Ber- 

 muda grass, 42 ; Johnson grass, 45 ; amber cane, 45 ; wild 

 hemp {Sesbania macrocarpa) , 75; Japanese rice, 36; Hon- 

 duras rice, 23 ; sugar beet, 16. No germination resulted with 

 such plants as oats, rye, corn, millet and Jerusalem com after 

 more than a few days' submergence. When the period of 

 submergence was extended to fifty days, the percentages of 

 germination were as follows: Bermuda grass, 14; Johnson 

 grass ,23; ambe rcane, 45; Honduras rice, 23; wild hemp 

 {Sesbania macrocarpa) , 13. One hundred per cent of rad- 

 dish, rutabaga, sugar beet and tomato seed, 75 per cent of 



