nybom: vegetatively propagated species 257 



found to lie between 1,000 and 2,000 r. The roots were also irradiated 

 in order to avoid excessive root shoot formation. 



In addition to reduced growth rate, the first shoots to appear 

 showed the expected primary effects, thick succulent leaves with 

 irregular margine and uneven surface. The author was well aware 

 that the mutations should be expected to form aberrant sectors in the 

 shoots formed, and that repeated bud and branch formation woidd be 

 necessary in order to isolate the changes in a pure condition. 



Therefore, the shoots formed were again decapitated and the 

 tips so obtained planted in order to form new roots. This process was 

 repeated as often as possible; in all, seven times between April and 

 June. The original 144 irradiated plants thus gave rise to 1,144 new 

 plants, which were allowed to grow undisturbed and which flowered 

 during October. Some changes in foliage were then noticed, as also 

 some types with possibly deviating flowering periods, late flowering 

 being a desirable character. 



In addition, a great many variations in flower color were 

 recorded, in all 281 different cases. Practically all of the originally 

 irradiated plants yielded such color changes, most of them a whole 

 series. The following new nuances were found: intensive rose, flesh- 

 colored, copper-rose, copper-red, cream-yellow to cream-rose, cream, 

 yellow, bronze, brown, red, and violet. White was obviously not 

 found. 



The new colors were either found as sectors in the flowers or as 

 single deviating flowers on a plant. Whole, changed plants were also 

 observed, mostly after the later decapitations; the early ones usually 

 giving narrow sectors. 



The percentage of recorded changes was highest after the highest 

 dose, 2.000 r. The author points out that it is important to use doses 

 that permit an extensive clonal propagation of the irradiated indi- 

 vidual in order to isolate the numerous changes induced at the 

 moment of irradiation. 



On the whole, Jank's results appear very impressive and promis- 

 ing, and he also summarized his work by stating that, "the experi- 

 mental induction of mutations by means of X-rays may be regarded 

 as an effective way of creating new color variations in Chrysanthem um 

 indicum" . 



