F. KiDi) AM) (\ West 11:} 



the previous \'ea]': or fa\'oiiral»le coiRlition.s (iiiriii«^ suniiuer niu}' fail to 

 increase the yield owing to adverse conditions which have previously 

 operated during the period of germination. It is such effects, namely 

 those which are to be traced to the environmental conditions which 

 have operated in the past stage of the plant's life, that we may term 

 effects of physiological pre-determination in order to mark theii' dis- 

 tinction from those which are due to hereditary causes. 



The present authors are engaged upon experimental work dealing 

 with the effect of various conditions acting upon seeds during Ijieir 

 maturation, dornuincy, and germination in pre-determining the course 

 of subsequent development and size of yield. Some preliminary results 

 have been communicated in a previous paper (Part I of this series(44)); 

 the present communication is a critical review of the literature bearing 

 directly or indirectly on the problem. 



It is interesting to note how exclusively attention has hitherto been 

 concentrated upon the isolated question of germination in the enormous 

 mass of literature dealing with the seed. In only a relatively small 

 number of cases has experimental work with seeds included observations 

 upon the subsequent course of development, nevertheless, the present 

 review indicates clearly the wideness of the field and the possibility of 

 obtaining important results if suitable experimental work on a sufficiently 

 large scale be carried out both in the field and in the laboratory. 



The most obvious categories under which we may deal with the 

 conditions affecting the "potentiality" of the seed, meaning by this 

 the capacity of the resulting plant for growth and yield, are as follows : 



I. Parental conditions, 



II. Harvesting conditions, 



III. Conditions during, or immediately preceding, germination, oi' 

 in the early stages of the seedling. 



CHAPTEK I 



PARENTAL CONDITIONS AFFECTING THE "POTENTIALITY" 

 OF THE SEEL*. 



A. Soil, Locality, and Climate. 



In considering cases which come under this category there is always 

 the difficulty of excluding the possible operation of hereditary factors 

 such as may make themselves obvious in the course of growth and 

 development as differences between forms of the same species, but do 

 not concern the question of physiological pre-determination. 



Ann. Biol, v 8 



