10 



The Plant World. 



development of organisms, their movements, distribution and 

 endemism, analogous to those already obtained in the studv of 

 the insular life of the oceans. Nevertheless, it is beginning to 

 appear that the facts of local distribution can be explained in 

 great part on the ground of immediate present day environment. 



INHERITANCE IN TOMATO HYBRIDS. 

 By H. L. Price and A. W. Drixkard, Jr. 



Evervone who is familiar with the rapid, sudden and marked 

 changes which have taken place in the family of cultivated toma- 

 toes during the brief period of its domestication will recognize in 

 the history of its improvement strong evidences in favor of the 

 view that the evolution of this plant, which has taken place 

 under domestication, has been wrought through a process of 

 mutation rather than by slow and continuous variation. The 

 stability of the characters which have appeared from time to 

 time gives further support to this view. 



In general it has been found that when mutants were crossed 

 with their parent forms the hybrids followed, in the inheritance 

 of particular pairs of characters, Mendel's law for inheritance. 

 The experiments discussed in this paper were undertaken pri- 

 marily with a view of testing this law for tomato characteristics. 

 In planning the experiments it was our aim to cover all of the 

 character units then recognized in the tomato, thus making the 

 work comprehensive so far as inheritance in this plant is con- 

 cerned. It was deemed more important to test the many pairs 

 of characters found in the tomato for dominance, particulate in- 

 heritance or blending in the F x hybrids, and for Mendelian splitting 

 or non-splitting in the F 2 generation, than to establish by a large 

 number of hybrids an exact correspondence to the theoretical 

 expectancv demanded by Mendel's law. The phenomena of 

 dominance and recessiveness, with subsequent segregation, are 

 quite sufficient to establish the fact of alternative inheritance; 

 and the absence of these phenomena is indicative of some other 

 mode of inheritance. Our main problem, therefore, was to de- 

 termine what form of inheritance existed for each particular 

 pair of tomato characteristics. 



The plan outlined at the inception of this work included 

 21 distinct crosses and many of these differed with respect to 



