Inheritance of Fasciation in Zea. 91 



findet die Umanderung in der sensiblen Periode der Jugend 

 statt, tevor das betreffende Merkmal sich ausbildet." * 



Whether such a juvenile sensitive period really exists in all 

 cases is a question. Undoubtedly it does when we are dealing 

 with annuals, as shown b}- the experiments of De Vries on 

 fasciations. It is a matter of fluctuating variability, to be com- 

 pared with the variation in the number of stigmatic ravs in 

 Paparcr Rhocas due to external conditions,! or the variation of 

 the number of ray flowers in Cenfaurea Cyanus,X Another in- 

 stance is yielded by the increase of the number of pistillodous 

 stamens, under favorable conditions, in Papaver somniferum 

 polycephalum. ** But since perennial plants may produce non- 

 fasciated inflorescences after having produced fasciated ones, as 

 in the case of Delphinium hybridum, the absence of the fasciation 

 can not be taken to mean a latency of the character due to un- 

 favorable conditions during the juvenile sensitive period. Or 

 are we perhaps to interpret the "juvenile sensitive period" as 

 referring to the earlier stages of development of a particular 

 part of the plant, i. e., that part in which the fasciation appears, 

 and not to those of the plant itself? Experiments are now being 

 conducted on the influence of unfavorable conditions in the early 

 stages of development on the percentage of fasciation in bien- 

 nials and perennials. 



Another instance of the latency of fasciation during one 

 generation is given by de Vriesft for Zea Mays, in which case the 

 latency probably was due to unfavorable conditions. But in 

 succeeding years, when the opposite was the case, he obtained a 

 comparatively high percentage (about 20% and 37%) cf fascia- 

 tions. Now it may be observed that a single corn plant may 

 produce both a fasciated and a non-fasciated ear. In our ex- 

 periments the following results were obtained : 



*loc. cit. 567. 



♦MacLeod, J. Over de veranderlykheid van het aantal stempelstralen by Papaver. Hand. 

 VI. IVai. en Gen. Congr.. 4: 11, 1900. 



♦MacLeod, J. Over de gevoelige periode van den invloed der voeding op het aantal 

 randbloemen by de korenbloem {Cenlaurea Cyamts). Hand. VI. Nat. en Gen. Congr., 



6: 420, 1902. 



♦de Vries, H. Plant-Breeding, 302. 1907. 



*de Vries, H. Over de erfelykheid der fascjatien. Bot. Jaarb. I odonea, 6: 94, 1894. 



