PLANT BREEDING 347 
interpretations need not bother us. Suffice it to say that most plant 
breeders have accepted the explanation that the recessive character 1s 
simply the lack or absence of the character in question, while the dom- 
inant character is its presence. ‘This is simply a slightly different in- 
terpretation of the same facts and simplifies some of the more complex 
results of crossing. Instead of 50 per cent. of the germ cells bearing 
the flint character and 50 per cent. bearing the sweet character when 
sweet corn is crossed with flint corn, one should think of all of the 
germ cells bearing the ability to produce the wrinkled sweet corn seeds, 
but that 50 per cent. of them contain in addition the presence of a flint 
or starch producing character. In other words, the “starchy” char- 
acter is superimposed upon the “ sweet ” character. The dominant and 
recessive characters in such a cross, then, are simply the presence and 
absence of the starchy character. 
When several character pairs differentiate the two parent plants in 
a cross, all possible recombinations are formed, the relative frequency 
with which the combinations occur being simply the algebraic product 
of as many of the simple ratios as there are character pairs. 
The importance of these Mendelian facts to the commercial plant 
breeder is great. In crossing plants differing in several simple char- 
acters that segregate after hybridization he may rest assured of two 
things. First, that with a sufficient number of progeny in the second 
hybrid generation, every possible recombination of the characters pres- 
ent will be represented by at least one pwre specimen. Second, that 
these pure specimens when selfed, or pollinated with their own pollen, 
will breed true. It should be remembered, however, that one may have 
to self a number of plants to get the combination desired with all 
characters pure, for if any dominant characters are concerned, their 
purity can be ascertained only by breeding for another generation. 
As an illustration we may take the snap dragon, Antirrhinum. There 
is a long series of colors that segregate. There is also a type called the 
“Delilah,” where the tube of the corolla is uncolored. Starting with 
this form in only one color, the whole color series of Delilah forms may 
be reproduced by crossing with the self colored strains. Or, one may 
combine the dwarf habit of growth of the Dwarf Champion tomato, 
with any of the various colors and shapes now on the market which 
have the ordinary tall habit of growth. Sometimes a very simple re- 
combination is of very great commercial value. The so-called Havana 
type of wrapper tobacco grown in the Connecticut River valley has 
large leaves and a short stocky habit of growth. It produces “from 
nineteen to twenty-one leaves. There is another type grown under 
cheese cloth shade which has a tall habit of growth with about twenty- 
six smaller leaves. ‘The tall slender habit of growth makes it an undesir- 
able type to grow in open fields where it is apt to be blown down, Mr. 
