350 THE POPULAR SCIENCE MONTHLY 

Fic. 7. Av tert “ HAVANA” PARENT, AT RIGHT “CUBAN” PARENT OF CROSS 
SHOWN IN Fic. 8. The “ Havana” has short habit of growth, large leaves averaging 
19 to 21 in number. The “ Cuban” has tall habit of growth and averages 26 medium- 
sized leaves. 
duction of a purple variety. When these two white varieties are crossed, 
the purple variety results. The second generation, however, produces 
seven whites to every nine purples. Such segregation into purples and 
whites may not be desirable; all purples may be wanted. This brings 
us to a consideration of class B of the four classes of phenomena at- 
tending hybridization, the production of desirable character combina- 
tions in the first hybrid generation and their continuation by asexual 
propagation. This class really includes several distinct types of oc- 
currences. The purple sweet pea produced from the two whites will 
serve as an illustration of the first type. In certain plants (not mean- 
ing the sweet pea, however) it is as simple to reproduce by cuttings as 
by seed. The cuttings are simply parts of the plant from which they 
come and are identical with it in character.? If in a species of this 
kind a desirable character is formed by the union of two or more 
hereditary factors and one wishes to reproduce the character indefi- 
nitely, asexual reproduction by cutting serves the purpose admirably. 
2'There are certain cases like variegation that are exceptions to this rule. 
