50 



DE. E. R. GATES— CONTRIBUTION TO A 



In the cross O. Lamarckiana x 0. rulricalyx, the Lamarchiana was from the P2 of 

 O. Lamarchiana X O. gigas. Its characters differed in no respects from O. Lamarchiana 

 of pure ancestry, and its guarded offspring also hred true. Its behaviour was, therefore, 

 in every way the same as that of pure 0. Lamarchiana. 



Again, when tw^o mutants from 0. Lamarchiana are crossed, O. Lamarchiana in 

 addition to one or both of the parent types is usually obtained in the Pj. Thus, the 

 cross O. ruhrinervis X O. nanella was made by DeVries four times, and in each case 

 the Fi showed only two types, O. Lamarchiana and O. ruhrinervis, the percentage of 

 the latter varying from 92 per cent, to 25 per cent. And in the one case in which 



ations of the cross were grown, the O. rtibrinerms of the Tj gave five types : 

 (1) 0. Lamarchiana^ whicli proved constant ; (2) O. riibtnnercis, which also bred true ; 

 (3) 0. nanella, whose constancy was not tested ; (4) an intermediate type, 0. nanella 

 rulrinervis, which bred true; and (5) 0. ruhrinervis, which in tbe P3 split again in the 

 same manner into O. Lama?x'hiana, O. ruhrinervis, and O. nanella ruhrinervis (see 



h + 



DeYries, Die Mutationstheorie, ii. p. 451). The constant intermediate type, O. ruhri- 

 nervis nanella, is virtually a much dwarfed O. ruhrinervis. The foliage is that of 

 O. ruhrinervis but the leaves are smaller. The amount of dwarfing is not so great 

 as in O. nanella, but it brings the plants much nearer the size of O. nanella than of 

 O. ruhrinervis. 



The crosses made between mutants also show that O. Lamarchiana as well as 

 one of the parent types appears in the Fj. O. nanella, however, is apparently an 

 exception as it rarely or never appears in the F^ the dwarf characters being recessive. 

 These results are grouped together in the second part of Table V. 



The sharp way in which the young seedling types are contrasted with each other 

 is clearly shown in PL 5. fig. 68. This pan contains the Fj from 0. lata x O. nanella. 

 Four of the seedlings (large and broad-leaved) are 0. Lamarchiana, two 0. ruhrinervis, 

 one O. lata (with crowded, broad, somewhat crinkled leaves and short petioles), one 

 (small) uncertain, and one new mutant having narrow, elongated, whitish leaves with 



very little chlorophyll. The latter soon died from lack of nourishment. 



1 



(b) Crosses with O. gigas. 



The results derived from crosses between the mutant O. gigas and other forms 

 have been somewhat conflicting, but I think all can now be brought under one view- 

 point without involving a contradiction. In the first place, O. gigas, when crossed 

 with O. Lamarchia/na, clearly differs from the other mutants in its behaviour, at 

 least in certain cases. DeYries first showed that O. gigas x 0. Lamarchiana and its 



procal give 



uniform hybrid type, intermediate between the parents 



He has since (1908) brought together the results of his crosses with this mutant 

 which may be summarized in the following table : 



