Abstract
Followmg the prevrous"The utilization of artificially induced polyploid plants in flower breeding"(1950), progenies of twelrty-eight polyploid speciesinduced bv colchicine treatment in 1948-'51 are beingarranged in Tables 1 and 2, showing the relativechange of external characters from original diploidsand the practical value under economic ctilture. Abilities of enlargaing flowers, increasing plant vigor andseed production, hasteningf lowering, strengtheningresistance against cold etc. are now becoming mainsubjects of discussion regard to thei utility. It isshown clearly that most of tetraploids having a fewchromosome numbers for intance, n=5-8 in thehaploid state such as cacalia, verbena, petunia, vincaand snapdragons, have manifested remarkably"Polyploid vigor"of plant growing with enlarged flowersand robust habit. Especially, the tetraploid giant double petunia is the finest flowers in all peturlias wehave ever seen. On the contrary, some tetraploids aslobelia and pansies possessed of a plenty of chromosome numbers in original state are much dwarfenedwith many slender or thickened stems and leaveshaving the same flowes as large as original plants.
