56 MAINE STATE COLLEGE 



Conclusion. 



From a study of the laws of heredit}', conclusions of vast im- 

 portance in the systematic amelioration of plants have been 

 reached. At the present time, however, but little is known of 

 the laws controlling the numerous secondary results attending the 

 crossing of plants. From the evidence at hand it appears that 

 the secondary results may be of fully as much importance as are 

 directly inherited qualities. 



There is little doubt that in a few important species there may 

 be an immediate apparent effect of foreign pollen on the female 

 organism of the current generation. It is equally certain, how- 

 ever, that the greater portion of food plants which have received 

 special study do not exhibit any immediate apparent effects of 

 foreign pollen ; while other species are still in dispute. 



That pollen has a direct stimulating effect on the ovary, inde- 

 pendently of its action on the ovules, seems a well established fact. 

 In many cases the size of the fruit is in direct proportion to the 

 amount of pollen used ; but it is also true that in many cases th ; 

 fruit may develop to a considerable degree, or even to its normal 

 size, in the entire absence of the male element. What the condi- 

 tions are which insure this phenomenon is as yet uncertain. 

 Exceedingly vigorous growth of the plant is certainly a first 

 requisite, but there also seems to be an individual variation in 

 this direction, with some species. 



Variations in the amount of pollen available, may to a large 

 extent determine the form and consequent value of the fruits of 

 some species. It is certain that in some instances — as with to- 

 matoes — the best practical results are obtained from an excessive 

 supply of pollen; while on the other hand, some fruits — as is 

 true of the English cucumber — may be of better form if pollen 

 is withheld. 



Whether superfoetation is possible, is a question of no small 

 importance, but the evidence is as yet insufficient for conclusions 

 to be drawn. 



With all cultivated plants there is a tendency to revert to an- 

 cestral forms, and it is important that this fact be borne in mind 

 in assigning definite causes to results obtained ; otherwise, erro- 

 neous conclusions will often be reached. 



