1920] Collins: Inbreeding and Crossbreeding in Crepis CapiUaris . 207 



MATERIAL AND METHODS 



Crepis capillaris is a species belonging to the chicory tribe of the 

 Compositae. The species is a native weed of European and North 

 African countries, and has been introduced into both North and South 

 America, where it grows in limited localities as a common weed. It 

 is either annual or biennial. The flowers are all perfect and both 

 cross and self-fertilization take place under natural conditions. In 

 nature it is quite variable in a number of ways according to the 

 environmental conditions in which it grows, but our breeding experi- 

 ments show that, when grown continuously under the same conditions, 

 constant forms are produced in successive generations. No records 

 have been found of its subjection to extensive artificial selection and 

 it is therefore, in the true meaning of the word, a wild species. 



In order to reduce the effect of variation in the environmental 

 factors of soil, light, temperature, moisture, and space to the minimum 

 care was taken to have the soil homogeneous, to have the same size 

 and kind of pots, and to grow successive generations of plants in the 

 same portion of the greenhouse as their parents had occupied. This 

 last item was varied in the last generation (1920) to the extent of 

 placing both inbred and hybrid cultures on a bench on the opposite 

 side of the greenhouse from the side where the parent cultures grew. 

 Inbred and hybrid cultures have been grown side by side. The ar- 

 rangement in plate 39, figure 1, and plate 40, figure 1, is that in which 

 the plants grew on the bench. Some of the inbred plants and some 

 of the crossbred plants were grown in both four and six-inch pots. 

 This did not alter the size and growth relations in any way. 



Crossing was accomplished in cultures 115 and 129 by emascu- 

 lation^ of the plants intended to be female parents, while in H-10 the 

 water- method of depollination was used. 



2 To be described iu detail in another paper. 



