Laboratory Work in Plant Breeding. 281 



in studying shape of squashes, bean seeds and the lil^e. In no other 

 way can he get so clear an idea of the variation that the particular 

 character exhibits in the various generations undor observation. 

 Later he should study the relation of one character to another. He 

 will run across numerous correlations, especially in color. The student 

 will soon find that it is often difficult to tell beforehand just what 

 characters behave as units in heredity. He might assume at the 

 beginning, for instance, that all the fibers present in a bean pod would 

 behave as a unit character, but this notion will be corrected when he 

 studies the second generation of a cross between a tough stringy- 

 podded bean and a tender stringless-podded one. He will at once 

 come upon plants with pods that have fibers along the sutures but no 

 fibers in the walls or perhaps pods that have the wall fibers without 

 the suture fibers. 



Laboratory Work in Selection. 



Practical work in selection is not well adapted to laboratory exer- 

 cises in a general course in plant breeding. There are a number of 

 plants or plant products that might be employed in such work. Prac- 

 tice might be had for instance in the selection of corn of a particular 

 type or some variety of table beet might be used instead. But such 

 work simply teaches the student what the desirable or standard char- 

 acteristics of a particular variety or crop are and affords him practice 

 in sorting out individuals of the approved type from those of that are 

 not so desirable. While this is most excellent ajid practical work it 

 manifestly belongs with the study of the particular crop in question 

 and should not be introduced to any great extent in a general plant- 

 . breeding course. 



When we undertake a laboratory study of the principles upon 

 which proper selection is based, much the same difficulties are encoun- 

 tered as we have to overcome in laboratory work with hybrids, namely 

 that large numbers of individuals must be used, requiring considerable 

 room and that several generations must be grown and studied, re- 

 quiring more time than the average student can afford. These diffi- 

 culties are to be met in the ways pointed out in discussing laboratory 

 work with hybrids: Small plants may be chosen; seed of several gener- 

 ations produced from a particular selection may be provided for the 

 student or, other individual plants of the various generations may in 

 some cases at least be propagated from cuttings; finally, preserved 

 materials may be employed. 



In a study of the results of a certain selection it is not enough that 

 the student see the type originally selected and note the progress made 



