336 



SCIENCE 



[N. S. Vol. XXVII. No. 6S7 



At the 1907 meeting of Section G of the 

 American Association for the Advancement 

 of Science I announced that certain results 

 had been obtained by exposing egg and 

 sperm cells of Onagra hiennis to radium 

 rays, and that these effects were character 

 changes that gave promise, if inherited, of 

 being of specific value. During the past 

 summer these plants matured, and seed has 

 been gathered for the F2 generation. Re- 

 sults in the F^ generation were in part as 

 follows : 



1. Funciional Asymmetry.^ One side of 

 the plants grew faster and more vigorously 

 than the other, though subjected to per- 

 fectly uniform environmental conditions. 



2. MorpJwlogical Asymmetry.— On one 

 side the leaves possess the characteristics, 

 not of the typical 0. biennis, but of one 

 of its mutants. 



3. A Plant having Two Shoot Systems 

 on One Boot. — One of these systems pos- 

 sessed the characteristics of the typical 

 iiennis, the other of one of its mutant 

 derivatives. This plant, and the mor- 

 phologically asymmetrical ones described 

 above, and interpreted as probably sec- 

 torial bud-sports, indicate a fundamentally 

 hybrid nature of the plants thus sporting. 

 The characters of the two diverse parents 

 separate out in the bud-sporting, and the 

 parental characters of one of the parents 

 have never found expression in a mature 

 ancestor in the direct line, but have existed 

 only potentially in the parental gamete. 

 Effect's of Radium Rays on Mitoses: Dr. 



C. S. Gager, New York Botanical Gar- 

 den. 



Root tips of Allium cepa were exposed 

 for various lengths of time to rays from 

 radium bromide contained in sealed glass 

 tubes. Exposure was made by placing 

 these tubes close to, but not touching, the 

 roots growing from bulbs in a moist cham- 

 ber. Thus the a rays were eliminated, only 

 the /8 and y rays being able to pass easily 



through the walls of the glass tube. For 

 purposes of comparison control (unex- 

 posed) tips, grown under precisely similar 

 conditions, except for the absence of the 

 rays, were collected at the same time as 

 those exposed. 



Examination showed various irregulari- 

 ties in the mitoses in roots exposed to the 

 rays. Exposure to the strongest radium 

 (1,500,000 activity) for a given period 

 completely inhibited nuclear division. 

 With less active preparations and varying 

 lengths of exposure there resulted various 

 disturbances to the chromosomes, some of 

 them lagging behind in the passage from 

 the equator to the poles of the spindle. At 

 times some of the chromosomes appeared to 

 have been accelerated in their passage, even 

 having gone beyond the poles. It was fre- 

 quently observed that some of the chromo- 

 somes failed entirely to pass to the poles, 

 and, consequently, were not included in the 

 formation of the daughter nuclei. This 

 elimination of chromatin from the daughter 

 cells may explain morphological changes in 

 a zygote, following exposure of the fusing 

 gametes to the rays. In one instance the 

 daughter nuclei have apparently separated 

 into two distinct parts, roughly giving the 

 appearance of two nuclei in each daughter 

 cell. 



The Relation of Bursa Eeegeri to Bursa 

 iursa-pastoi-is : Dr. G. H. Shull, Sta- 

 tion for Experimental Evolution. 

 Before the beginning of my experiments 

 Bursa Eeegeri was known with but one 

 type of rosette, apparently agreeing with 

 one of the elementary forms of Bursa 

 hursa-pastoris which I had previously 

 shown to possess two dominant Mendelian 

 units in the lobing of its leaves. Upon 

 crossing B. Heegeri with that form of B. 

 iursa-pastoris which had the correspond- 

 ing recessive characters, the second genera- 

 tion showed the same four types of rosette, 

 previously secured in a cross between the 



