528 Cannon : Studies in Plant Hybrids : 



Express x Serpette 



Like Fillbasket x Debarbieux, this is a second generation hybrid, 

 and it also, as has been described in a preceding paragraph, shows 

 the sphtting into several types after the law of Mendel. The re- 

 version of Express x Serpette as regards the quality of size and 

 form of the plants is fairly well indicated by/. 34-37, where the 

 pure parents are also represented. It should be noted that the 

 sketches are drawings from photographs and that the plants were 

 photographed at the same time and under precisely the same con- 

 ditions, so that the figures faithfully reproduce the relative forms 

 and sizes of all of the plants. 



The sporogeny of Express x Serpette corresponds closely in 

 the points examined to that of Fillbasket x Debarbieux, although 

 in certain regards, which will be indicated, a difference between the 

 two was noted. Also some phases of development were repre- 

 sented in my preparations of Express x Serpette, not found in 

 those of the other hybrid, and these will be mentioned, in addition 

 to the preceding, rather than a more complete account. By this 

 method I shall avoid unnecessary duplication ; the two hybrids 

 are so nearly alike in the matter of spore origin and development 

 that a description of these processes in the one would for the most 

 part answer perfectly well for the other. 



The series representing the nuclear divisions in young anthers 

 was not so complete in Express x Serpette as in Fillbasket x De- 

 barbieux, and possibly for this reason I have not so complete evi- 

 dence of the association of the chromosomes in pairs in the last 

 sporogenous division in the former as in the latter hybrid. It 

 was observed, however. An apparently good example of the 

 pairing was seen where perhaps one would not expect it, namely, 

 in the division by which the sporangial wall is separated from the 

 inner sporiferous tissue. The outer cell resulting from this division 

 by further division gives rise to three series of cells, the inner of 

 which forms the tapetum ; the inner cell of the division noted be- 

 comes converted without further division into a spore mother-cell. 

 The division referred to occurs rather late in the pea. Both of 

 the nuclei resulting from this division had their chromosomes ar- 

 ranged in twos. If the curious association of the chromosomes 



