192 University of California Publications in Agricultural Sciences [Vol. 2 



will be reported later. But before confining our attention too largely 

 to one or two species only, it was deemed advisable to look into the 

 possibility of obtaining fertile hybrids between these species. 



Although the species in question show differences in many morpho- 

 logical characters and in at least one physiological character, only 

 those having to do with the seedling stage will be considered here, 

 due to the fact that the hybrids in all cases died during this stage. 



The achenes of Crcpis capiUaris range in length between 2.0 and 

 2.5 mm. ; they have no beak, and the pappus sheds rather easily. The 

 cotyledons vary from broadly ovate to the condition where the breadth 

 of the widest part is greater than the length, in which case the tip of 

 the cotyledon is distinctly dentate. The first plumule leaf makes its 

 appearance very quickly after the cotyledons have expanded to their 

 normal size. The cotyledons are approximately 5 mm. wide and 

 4 to 6 mm. long (pi. 36, fig. 2). 



The achenes of Crepis tectorum range from 3.5 to 4 mm. in length 

 and are correspondingly thicker than the capiUaris achenes. The 

 tectorum achenes are also beakless but they retain their pappus more 

 persistently than do those of the other species. The cotyledons are 

 distinctly different in both shape and size. The general shape is nar- 

 rowly linear with bluntly pointed ends. Length of cotyledons varies 

 around 6 mm., the width around 3 mm. As in capiUaris, the plumule 

 leaves appear very promptly, usually one at a time, but occasionally 

 in both species two plumule leaves appear simultaneou.sly. Thus there 

 is evident a distinct difference in size and shape of the first or cotyledon 

 leaves of the two species corresponding with the difference in size of 

 achenes, and a resemblance in the prompt appearance of the plumule 

 leaves (pi. 36, fig. 1). 



Crepis tectorum possesses one more pair of chromosomes than C. 

 capiUaris, the former having four pairs, the latter, three pairs (pi. 38, 

 fig. 2). 



Two methods of pollination were employed, which will be descrilxd 

 in detail in another paper: (1) Emasculation of female parent flowers; 

 (2) female parent not emasculated but washed free of its own pollen 

 by use of a fine jet of water. The second method was used when the 

 capiUaris plant had given indications from selfing tests of being self- 

 sterile. The results of cultures thus secured are indicated below. The 

 female parent is mentioned first in each cross. 



