Kraus: The Self-Sterility Problem 



557 



points to a phase of the pollination and 

 fertility investigations that have not 

 received the attention they merit; 

 namely, a thorough study of the vas- 

 cular system of fruits. There certainly 

 are varying degrees of interdependence 

 of seed and flesh formation. This 

 absolute dependence of some varieties 

 upon the presence of seeds in order to 

 reach maturity and the absolute inde- 

 pendence of others raises a series of 

 questions which as yet are not under- 

 stood but deserve careful attention. 

 Of course, they may have a more direct 

 bearing in the problems of self-fruit- 

 fulness and parthenocarpy, but they 

 are by no means to be disregarded in 

 solving the problem of self -sterility. 



STUDY OF THE CELL 



The further study of the' phenomena 

 of gametogenesis and fertilization, es- 

 pecially as related to nutrition, is 

 absolutely essential. Coulter's recent 

 contribution on reproduction in plants, 

 especially that portion which deals with 

 the conditions under which gametes are 

 formed, is most suggestive in this latter 

 regard. Much more information is 

 needed on nutrition and its relation to 

 embryo development, and the inter- 

 relation of vegetative or somatic vigor 

 to reproductive vigor. Cannot the one 

 be measured in terms of the other to a 

 considerable degree ? The possibility of 

 changing certain varieties from a self- 

 sterile condition to a so-called self- 

 fertile one by a change in nutrition is too 



well known to require more than 

 mention, but the fact should not be 

 overlooked that in the great majority 

 of such cases actual self-fertility has not 

 been induced but rather a condition of 

 self-fruitfulness. In many varieties of 

 apples, it is possible to bring about self- 

 fruitfulness (without plump seeds) by a 

 change in nutrition and self-pollination; 

 it is much more difficult to do so when 

 no pollination takes place. It seems 

 that a stimulation of the ovules must 

 be induced, and this stimulation trans- 

 mitted to the vascular system ; and that 

 when a "tendency to develop" has been 

 set up, the fruit continues to develop 

 whether seeds are present or not. A 

 greater expression of this "tendency to 

 develop" is evident when fruit is pro- 

 duced without pollination, but some 

 other abnormal condition of nutrition 

 or stimulation has been applied to bring 

 about the result. Its greatest expres- 

 sion is the production of fruit, normally 

 parthenocarpic ; a phenomenon purely 

 vegetative in character, neither pollina- 

 tion nor abnormal stimulation having 

 been required. It may be argued that 

 the term "tendency to develop" explains 

 nothing. Granted ; however, it expresses 

 an existing condition or relation, the 

 fuller explanation of which will come 

 from a more thorough study of vegeta- 

 tive parts, and a correlation of their 

 structure and developmental behavior 

 with fertilization and seed production, 

 whether such correlation be positive or 

 negative. 



Home-grown or Foreign Seed 



At the Maine Agricultural Experiment Station studies on inheritance in oats 

 and beans, having regard to yield, color, and other characters, have been under way 

 for some years; cross-bred apples are being studied, and the effect of selection in 

 populations and pure lines is also the subject of investigation. In view of the 

 importance of the oat crop in the state, that cereal has been given special attention, 

 with the view of securing the best possible varieties for local conditions. The 

 work was begun by a careful test of the varieties already in use, and continued by 

 isolation of pure lines and by hybridization. The current idea among farmers 

 that foreign-grown seed is better than home grown, has been found here, as else- 

 where, to have Httle basis; frequently, indeed, a variety behaves much better after 

 it has been acclimatized for a vear or two. 



