248 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 



Onagra biennis Onagra jc 



Erect, generally stout, annual or Rosette leaves finely and sparingly 



biennial, simple and wand-like or pubescent, the larger ones i 2-14 cm. 



branched, i°-9° high, more or less long; blades narrowly linear-lanceo- 



hii^sute-pubescent, rarely glabrate. late, acuminate at both ends, undu- 



Leaves lanceolate, acute or acumi- late, much longer than the j^etioles ; 



nate, narrowed and sessile at the stems 7 dm. tall, with several rather 



base or the lowest petioled, repand- large ascending branches below the 



denticulate, i'-6' long; flowers spi- middle ; stem-leaves drooping ; blades 



cate, terminal, leafy-bracted, bright almost linear, often narrowly so, 



yellow, open in the evening, 1-2' tapering to both ends, entire ; bracts 



broad; calyx-tube slender, much similar to the stem-leaves, but slightly 



longer than the ovary, the lobes smaller; hypanthium about 40 mm. 



linear, contiguous at the base, re- long; sepals about 20 mm. long, 



flexed; capsules oblong, narrow fully one half as long as the free 



above, erect, pubescent, %'-i' long, portion of the hypanthium, the free 



2>^"-3" thick, nearly terete, seeds tips in the bud stout, 2.5-3 "'"^• 



angled. long; petals about 15 mm. long, 



retuse at the apex. 



Why, in the two aberrant plants described above, the entire speci- 

 men showed the changed characters, instead of one half only, as in 

 the case of the morphologically asymmetrical specimen, cannot of 

 course be said. Possibly the pollen-grains were differently affected 

 in the different exposures to the rays, possibly, and quite probably, 

 the mitoses that followed fertilization were different, resulting in the 

 one instance in a segregation of the parental chromatins, but not so 

 in the other case, or possibly the eggs that were fertilized by the 

 irradiated pollen were unlike, or there may have been a combination 

 of any two or of all three of these possibilities. Attention should 

 also be called to the fact that these aberrant forms may not be results 

 produced by the rays of radium, but only spontaneous mutations, 

 whose cycle happened to coincide with the time of the experiment. 



Of far greater interest were the two plants illustrated respectively 

 in PLATE ID {loa of my cultures), and plate ii (ii<!; of my cul- 

 tures). These plants are as unlike each other as they are different 

 from the parent biennis^ or any of its hitherto observed mutants. 

 The seed that produced loa came from a capsule exposed after pol- 

 lination with unexposed pollen for 53 hours to rays from radium 

 bromide of 10,000 activity. Both sperm- and egg-cells, therefore, 

 were exposed to the rays. A description of the plant follows : 



