I 



Oil the Vitalitii of Farm Seeds. 171 



What causes the death of the seed ? Under the protection 

 of the seed-coat there is an emljryo plant with a supply of food 

 sufficient to support it when it begins its active life. The 

 enil)ryo plant consists of a short stem, bearing one or two leaves 

 at its apex and a minute rootlet at its base. Among the 

 varieties of seeds experimented upon, clovers and turnips have 

 the necessary food stored in the tissues of the embryo plant, 

 bnt in the cereals and pasture grasses and in carrot and yarrow 

 the small embryo plant has its food stored beside it within the 

 seed-coat. The embryo is the essential element in the seed ; it 

 alone possesses vital force. It has within itself, even in the 

 cereals and seeds like them, sufficient food for the earliest 

 stages of growth. If separated from the store of food outside 

 it, the small embryo of wheat can grow to several times its own 

 length. The store of food is not alive, nor is it moditied by the 

 death of the embryo ; it remains unaltered ])oth chemically and 

 physiologically for a long time. Moistening seeds that had 

 been dead for six years, and removing the dead embryo, I have 

 placed the embryo of a living plant in the cavity left by the 

 removal, and seen it appropriate the stored food as effectively 

 for its own growth as embryos that were tested while still in 

 their natural position. 



The emln-yo remains dormant until the heat and moisture 

 necessary to start it into active life are available. Generally 

 the seed has a period of rest. Seeds produced early in the 

 season remain as a rule unafl'ected by the moistvire and heat of 

 summer and autumn. Not till the following spring do they 

 begin their active life. But some seeds germinate in the yeai- 

 in which they are produced. The farmer, to his cost, knows 

 this when his wheat is blown down and, a wet season supplying 

 the needed moisture, the grains germinate while still in the 

 ear. Moisture without heat, or heat without moisture, will fail 

 to make the seed germinate. The seeds of 1895 experimented 

 upon had, throughout the years they were in my cabinet, a 

 temperature sufficient for germination, but the moisture was 

 wanting. Seeds buried too low in the ground fail to germinate 

 l)ecause, though they have sufficient moisture, they do not 

 receive the necessary heat. Mr. F. Stratton, F.L.S., has just 

 told me of the appearance in enormotis quantities of the 

 water chickweed on an emliankment made with river sediment 

 from the banks of the Medina, in the Isle of Wight, in which 

 the seeds must have been resting for not less than twenty 

 years. 



If a seed is to retain its life, moisture must be present in 

 the embryo plant. Loss of moisture beyond a certain point, 

 whether it occurs rapidly or gradually, means the death of the 

 seed. Temperature may be varied within very wide limits 



