PLANT PHYSIOLOGY 217 



from every conceivable aspect during the last century, the 

 physiology of reproduction has received only slight attention, 

 although from the economic point of view this may be relatively 

 of considerably greater importance. During the last few years 

 this discrepancy between the amount of work devoted to the 

 vegetative body and the reproductive organs from the 

 physiological point of view has to some extent disappeared, 

 and it is not surprising that the greater proportion of the work 

 dealing with fruit formation should have been done in insti- 

 tutions devoted to investigations in agriculture and horti- 

 culture having an economic significance. 



That the composition of the soil has an important influence 

 on the production of fruit was noted and commented on by 

 many earlier observers, including Charles Darwin, who devoted 

 some attention to this question in his Variation of Animals 

 and Plants under Domestication. Further observations on 

 this question have been recorded recently. Thus J. Farrell 

 (Journ. Agric. Victoria, 15, 142, 191 7) found thst the Jonathan 

 apple is usually more or less self-sterile on soils in Victoria 

 rich in nutrient substances, while on poor soils it becomes 

 self- fruitful. The reverse phenomenon seems to be the case 

 with an American grape (" Hope "), which only produces 

 hermaphrodite flowers when carefully cultivated, the gynaecium 

 becoming functionless if the culture is poor. 



How far particular nutrient substances in the soil influence 

 the formation of flower buds and the subsequent production 

 of fruit is in considerable doubt. Some evidence appears to 

 be accumulating to the effect that the addition to the soil 

 of fertilisers containing nitrogen, such as sodium nitrate, 

 increases not only the num-ber of flowering short shoots 

 (" spurs ") in apples, but also the percentage of flowers which 

 produce fruit (C. C. Wiggans, " Some Factors Favouring or 

 Opposing Fruitfulness in Apples," Missouri Agric. Sta. Res. 

 Bull., 32, 60 pp., 191 8), and a high nitrogen content in the 

 spur itself certainly appears to further the production of fruit 

 from the flowers (E. M. Harvey and A. E. Murneek, Oregon 

 Agric. Exper. Sta. Bull., 176, 1921). 



There can be no doubt whatever of the influence of climate 

 on the production of flowers and fruit, although it may not 

 always be easy to determine which factors of the environ- 

 ment are those particularly responsible for any observed effect. 

 M. J. Dorsey (" Relation of Weather to Fruitfulness in the 

 Plum," Journ. Agric. Res., 17, 103-26, 1919) found that low 

 temperature and excessive rain are the climatic factors which 

 influence most unfavourably the setting of fruit in the plum. 

 Low temperature brings about retardation of growth of 

 the pollen tubes, the time required for the pollen grain to 



