88 maine; agricultural lxplrimlnt station. 1904. 



to unite. Gould 1 reported a similar case where crookneck squash 

 was pollinated with bush scallop. There was a vigorous develop- 

 ment of pollen tubes, since they passed in the vicinity of the 

 ovules, but there was no fusion of the nuclei. 



SUMMARY. 



In summarizing those cases in which reciprocal crosses have 

 failed, we may note that in some cases pollen tubes do not 

 develop, in others there is a partial germination, and in others 

 still there is a vigorous development of tubes ; but in none of 

 these cases is there fusion of the nuclei. 



II. Studies by thl Author. 



A. RLD CURRANT AND YLLLOW PLUM TOMATO. 



The difficulty which has been experienced in making recipro- 

 cal crosses with red currant tomato, Lycopersicum pimpinelli- 

 folium, and varieties of Lycopersicum esculentum, has given rise 

 to the notion that such reciprocals cannot be made. Wishing to 

 know the facts in the case, the writer began investigations with 

 the following points in view. First, to see if reciprocal crosses 

 with these plants can be made. And secondly, if this is impos- 

 sible, to find out what constitutes the difficulty. 



Plants for this work were grown in the University greenhouse. 

 Seeds of yellow plum and red currant tomatoes were planted in 

 flats, and as the seedlings attained proper size they were trans- 

 planted, some into large pots and others into large boxes. As 

 soon as the blossoms appeared, a study of the sexual elements 

 was begun. For the first few weeks following the appearance of 

 the flowers, much time was spent in a study of the pollen of 

 these plants. The results of this investigation are given below. 



(1.) A comparison of pollen. 



In attempting to account for failure in crosses, one is apt to 

 consider pollen as the source of trouble. In view of this fact, a 

 structural and germinative study of pollen was made. Pollen 

 from flowers of the kinds mentioned above was examined in dry 

 and fluid mounts, but no differences in form or structure could 

 be detected. Although the pollen from both species was to all 



1. H. P. Gould, Studies in Potency of Pollen, Cornell Univ. Thesis, 1897. 



