Presumptive Mutations in Wild & Cultivated Plants 63 



In a study of the variations of tobacco in the East Indies, 

 LodewijUs (1911) states that double flowers are the most common 

 aberrations, although gigantism, fasciation and other types of 

 change also occur. Doubles appear yearly on almost every 

 plantation, and the doubling is of the hose-in-hose type. All parts 

 of the plant are also changed, so that doubles can easily be 

 distinguished before they come into bloom. The stem is zig-zag, 

 shorter and not winged ; the leaves are very small and thicker 

 owing to local outgrowths on their ventral surface ; the midrib is 

 twisted, and the stigma shows similar growths, though to a less 

 extent. All these peculiarities apparently result from a single 

 mutation, and the type breeds true. In crosses with the normal the 

 latter dominates almost without exception, and the F a gives a 3 : 1 

 ratio (46S : 10D, 306S : 105D). It is a curious fact that the 

 heterozygotes were distinguishable from pure singles by their 

 leaves having outgrowths on the underside. Thus of the 306 

 singles above, 204 were shown in this way to be heterozygous and 

 102 SS. Again, in the F 2 from single X double the ratio was 

 32S : 58DS : 31 D. It is very interesting that in this set of 

 mutant characters, the double flowers are wholly recessive and 

 the leaf peculiarity at least partially dominant, though they behave 

 as a unit in inheritance. 



In a work on the mountain cherries of Japan, in which is 

 embodied an elaborate study of the group of plants which plays 

 such a prominent part in the national life of that country, Miyoshi 

 (1916) recognizes four species, Pninus serrulata Lindl., P. mutabilis 

 Miyos., P. sachalinensis (Fr. Schm.) Miyos., and P . fruticosa Miyos., 

 and a very large number of forms, especially of mutabilis (65) and 

 serrulata (68). Cultivated double varieties have been known for 

 over a thousand years. A great number of forms have arisen in the 

 intervening period, but only the best have been preserved and 

 many old varieties have been lost. In Yoshino, the oldest and 

 most famous cherry neighbourhood, trees have from time to time 

 been planted from the neighbouring mountains for over a 

 thousand years. At Koganei, near Tokyo, is the greatest assemblage 

 of wild cherries, none of which show any influence of cultivation. 

 There are three other main centres for cherry varieties, and many 

 places noted for a local form or even a single tree, but the larger 

 centres have been the source of new forms and races from time 

 immemorial. 



