THE PHENOMENA OF REVERSION 343 



were formed. It seems only possible to explain this circumstance 

 by supposing that the connection of the two idioplasms was 

 easily severed, and that differential nuclear divisions occurred 

 in such a manner as to cause a larger number of idants of 

 C. purpiu'CHs to pass into one daughter-nucleus, and a larger 

 number of those of C. laburmini into the other ; or, at any rate, 

 to cause the one or the other idant to pass completely into one 

 of the daughter-nuclei, instead of dividing longitudinally and 

 one of the resultant halves entering each daughter-nucleus. 

 Though this is certainly only a conjecture, it is, however, not 

 altogether an unjustifiable one, for the apparatus for division in 

 each of the two species is certainly concerned with a smaller 

 number of idants than that which must be present after the 

 fusion of two nuclei ; irregularity might therefore easily occur at 

 the division. It is possible that unknown forces of attraction 

 may also play a part in the process : the idioplasms of the two 

 species do not at any rate exhibit a marked attraction to one 

 another, as might perhaps be conjectured from the negative 

 results obtained by Darwin, Reisseck, and Caspary in ordinary 

 experiments on hybridising. By fertilising C. labiirmiin with 

 the pollen of C. purpiireiis^ Darwin obtained pods which dropped 

 off ' in sixteen davs after the withering of the flowers,'' and the 

 reverse cross resulted even less successfully. 



However this may be, — and the point can be settled by deter- 

 mining the number of idants, — the phenomena of heredity at 

 any rate indicate that the idioplasms of the two parents . can 

 easily again become separated in the course of cell-divisions. 

 This separation might perhaps begin with the passing over of 

 one idant only from one side, which would result in the pre- 

 ponderance of one parent in many of the blossoms, &c. This 

 preponderance would have increased considerably in the course 

 of growth, so that far larger groups of cells now frequently con- 

 tain pure idioplasm of C. laburtinin or C. pnrpureus, and new 

 shoots are formed which apparently contain idioplasm of one 

 or the other species only. The fact that the plants raised by 

 Herbert from seeds of pure yellow flowers oiCytisiis adanii. which, 

 although they bore yellow flowers, showed a purple tinge on the 

 flower stalks, proves that even these shoots may still contain 

 some individual idants of the other ancestral species. The 

 idants of C. pm-pureus seem, however, to have disappeared 

 entirely from certain shoots ; for Darwin raised plants from 



