A. B. Stout 117 



first few years in my culture plants of this variety ranged from 4^ to 6| 

 feet in height and were quite uniform in general appearance. The 

 occasional degenerate plant was always one of the smaller plants. No 

 controlled pollinations were made for such plants and they were not 

 included with self-incompatible plants. 



It has also been observed that abnormalities may be present in the 

 pollen giving grains of noticeably large size. Cytological preparations 

 show that these giant pollen grains are due to the incomplete separation 

 of the four daughter cells that result from the reduction division. 

 Quadripartition is arrested and a spore wall is formed about all four 

 daughter nuclei. In some cases the giant grain is decidedly lobed. 

 Such irregularities in the development of pollen have not been observed 

 in other stocks (wild, Barbe de Capucin, and hybrid generations) in 

 which examination of much pollen has been made. The proportion of 

 giant grains has not been large and they have been found in largest 

 numbers among highly self-compatible and incompatible plants indis- 

 criminately. For many self-incompatible plants, giant grains were 

 absent or rare. Thus it would seem that their development has no 

 connection with incompatibilities, but is rather associated with the 

 conditions of duplication and cohesion which are characteristic of this 

 variety as described elsewhere (1918 b). 



The three highly self-compatible plants selected as parents of the /, 

 gave progenies that were decidedly different in regard to vegetative 

 vigour and potentiality for seed production. One line of descent was 

 decidedly degenerate, the others were highly vigorous in growth and in 

 sex vigour. 



1. A degenerate line of descent. One of the parent plants, R 9 No. 84-, 

 was 4| feet tall, well branched and exhibited no signs of degeneracy. 

 Its main axis was strongly duplicated and there were lesions and con- 

 siderable torsion quite as illustrated in a former paper on this type 

 fasciation (see No. 9 of Plate XII, 1918 b). Giant pollen grains were 

 frequent, but the plant w^as decidedly self-compatible and set abundant 

 seed to open pollination. 



The series {R 9-3Jp- ) grown from its seed was noticeably low in 

 vegetative vigour. No plant was more than 5^ feet tall ; few were more 

 than 5 feet ; numerous plants were only from 3 to 4^ feet in height and 

 some were but 2 feet tall. Many plants produced very few seed to open 

 pollination and some produced no seed at all. Such impotent plants, 

 about 40 in number, were not included in the self-incompatible plants 

 recorded for this series. 



Joum. of Gen. ix 8 



