222 PIn/siolof/ical Pre-determination 



seed-treatments. When once the position is defined it becomes apparent 

 that such tests might give positive results, and, if so, would be of con- 

 siderable practical value owing to the simplicity, brevity, and cheapness 

 of the operations involved. 



In the following review we shall have to deal with a very wide range 

 uf seed-treatments. It therefore seems advisable to briefly consider, 

 under the headings of the various arbitrary methods employed, the 

 results which have been reported in the literature, and subsequently 

 to deduce as far as possible our general conclusions from the whole of 

 the available evidence. 



Treatments of the Seed affecting the Nutrition of the Seedling. 



We may classify the treatments affecting nutrition and deal with 

 them under the following headings: 



{a) Removal or Partial Removal of the Cotyledons, Endosperm, 



etc. 

 (6) Soaking Treatments; 

 (c) Seed Impregnation Treatments {i.e. treatments in which the 



seeds are soaked in solutions of nutrient salts) ; 

 {(l) Enzyme Treatments. 



{a) Removal or Partial Removal of the Cotyledons, Endosperm, etc. 



An obvious method of varying the amount of reserve food-material 

 available for the developing embryo has been to remove, or partially 

 remove, the cotyledons of exalbuminous seeds or the endosperm of 

 albuminous seeds. In this way series of plants with decreasing initial 

 supplies of food-material available for the seedling have been compared 

 with plants from untreated seeds. But it should be borne in mind that 

 not only have the food-reserves been removed with the cotyledons, but 

 also a certain proportion of the initial assimilating surface of the plant. 

 This factor appears to have been entirely overlooked by the original 

 workers. 



Experiments conducted on these lines are worthy of considerable 

 attention tor although the treated seeds do not, of course, give results 

 showing increased yields, yet they clearly demonstrate the potentiality 

 for pre-determination which exists during the early stages in the develop- 

 ment of the seedling. The effects of the amount of nutrient material 

 originally available foi- the embryo are found in the case of annuals to 

 last throughout the life of the plant, and to be cleaily visible during the 

 stages of vegetative development, of flowering, and of seeding. 



