Laboratory Work in Plant Breeding. 27t> 



Difficulties Encountered in a Laboratory Study of Hybrids. 



When it comes to studying results of hybridization in the labor- 

 atory many difficulties arise. In the first place at least three genera- 

 tions of the hybrid in addition to the parent generation must be grown 

 in order that the student get an adequate notion of the behavior of 

 hybrids. This is not a difficult matter for the special student who 

 will spend some years in the work; but in the one or two semesters 

 which the average student can devote to the subject there is not time 

 to grow four genrations one after the other of any plant with which 

 I am acquainted. The early dwarf beans require comparatively little 

 time for development, usually not much over three months from the 

 time the seed is planted until the crop is ripe, and yet, if no time is 

 lost during the nine months of the school year, the student can barely 

 grow the parent races, cross them and grow the first and second gener- 

 ations of the hybrid. One way around this difficulty is to have on 

 hand from a previous year's work crossed seeds and seeds of the first 

 and second generation of the same hybrid. The student can then 

 at the very beginning of his course plant seeds of the pure parents races 

 and seeds that will produce the first, second and third generations of 

 a particular hybrid. Or the difficulty may be overcome by choosing 

 a plant that can be propagated by cuttage or some similar means as 

 petunia or tomato for instance. Individuals of several generations of 

 a hybrid, once they have been obtained, can then be carried along 

 from year to year without great trouble. The advantages of these 

 methods are that they enable the student to compare the several gen- 

 erations of the hybrid directly with each other and to complete the 

 work in a single semester. The main disadvantage of the methods 

 is the fact that the student will take less interest in the study of "ready 

 made" hybrids than in following his own crosses from one year to 

 another. 



A method not very different from those already suggested is to 

 use preserved materials. Of all these, specimens on herbarium sheets 

 or in glass jars are of least value. The choice should be for plants, 

 some product which will keep well in its natural state. Ears of corn 

 are ideal in this respect. The same specimens can be kept for a long 

 time if carefully handled. Seeds of beans, peas, etc., are also good. 

 Gourds, I suppose would furnish excellent material. But hybrid speci- 

 mens need not be limited to products that keep for years. Even 

 pumpkins and squashes, excellent subjects for crossing, can be kept 

 ' 'well through the winter. Some of the ornamental gourds can be kept 



