62 Mutations and Evolution. 



a strongly double red form. A double Anemone Pulsatilla is 

 figured by Helwing as early as 1719. Doubling is well-known to be of 

 frequent occurrence in the Ranunculaceae. A Convolvulus sepium 

 with double flowers is described from New Brunswick, New Jersey. 1 



An interesting record is that of Sagitturia variabilis? Engelm., 

 a large patch of which, on an island in the Susquehanna, had 

 completely double flowers. All the carpels of pistillate flowers and 

 all the stamens of staminate flowers were converted into petals, 

 giving the flowers the appearance of tiny snowballs. This 

 probably represented a single individual mutation which had 

 spread from rootstocks Elsewhere (Gates, 1917b) we have 

 assembled numerous records of doubling in Trillium grandiflorum, 

 the same root stock producing each year a double flower. There 

 are various interesting records of double wild Rhododendrons. 

 Rehder (1907) found in the woods at Glacier, British Columbia, a 

 bush of E. albiflorum Hook, with double flowers. It was growing 

 among normal bushes. In the double flowers, petalody of the 

 stamens was combined with an increase in the number of staminal 

 whorls. In the Alps, R, ferrugineum has been observed at least 

 twice with double flowers, Kerner having found a large number of 

 such shrubs in one locality. Miyoshi (1910) has described the 

 occurrence of doubles in R. brachycarpum Don. The double form 

 is called var. Nemotoi Makino. In the location (on a volcanic 

 mountain) where it was found both white and rose varieties occur, 

 but only the white showed doubling. Seven plants were observed 

 with double flowers and ten with normal. In another place a 

 group of five bushes was found, all with double white flowers. 

 Nakai 3 found double and white varieties of R. Kaempferi in the 

 vicinity of Karume, Japan. 



That cultivation does not produce doubling, even in a genus 

 where doubles occur wild as mutations, is clear from the case of 

 R. Metternichii, which is much cultivated in Japan but no double 

 is known. If there is any relation between the environment and 

 the occurrence of mutations in this genus, it remains elusive, as in 

 most other organisms. We still have no better term than 

 " spontaneous " to apply to it. 



Makino 4 cites also the finding of one double Oxalis corniculata, 

 and Deutzia scabra entirely double in a locality in Nikko. 



1 Bull. Torrey Bot. Club, 17 : 238. 1890. 



1 Porter, Thos. C., Bot. Gazette 1 : 5, 1875. 



Bot. Mag. Tokyo, 29: 261, 1915. 



4 Journ. Coll. Sci. Tokyo, 1910. 



