HYBRIDIZATION OF WILD PLANTS 
D. T. MacDoucaL 
(WITH FOUR FIGURES) 
THE number of forms of plants which have been or are regarded as 
hybrids by systematists is a large one and includes several oaks, 
of which two have been examined during the last two seasons. Atten- 
tion has been called previously to the untrustworthiness of the custom 
prevalent among botanists of attributing a hybrid origin to certain 
plants because they appear to exhibit halved, fused characters, or 
@ mosaic of qualities derived from the two suppositious ancestors. 
In some instances such deductions have been made by which the 
ancestry of a questionable plant has been made to include three or 
even four species. The argument of distribution is the main one 
offered in such attempted demonstrations. In many cases, this 
together with other circumstantial evidence may amount to almost 
Positive conviction, but unless this close relation of well-joined facts 
is furnished, assertions as to the hybridity of a plant must be taken 
simply as a suggestion to be tested by cultural or experimental 
methods. 
When confronted with an enigmatical plant of such character, three 
methods of attack are available to the investigator: that of obtaining 
the. supposed hybrid by synthetizing it from its supposed parents; 
that of making an anatomical examination of the hybrid and the 
parents to which it has been referred; and that of obtaining second, 
third, and succeeding generations of the hybrid for the purpose of 
ascertaining whether or not any separation of the ancestral char- 
acters may occur in an alternative inheritance by which the ancestral 
forms may actually reappear. All of these methods are beset with 
numerous difficulties, but when used together with the facts of dis- 
tribution a very satisfactory degree of proof may be obtained. It 
will be profitable to consider the scope and application of the various 
methods of experimentation and observation noted above. 
* Read before Sections F and G, A. A. A. S., New York City, December 27, 1906. 
45] [Botanical Gazette, vol. 43 
