382 University of California Publications in AgricuUunil Sciences [Vol. 2 



types were as follows (the capital letters. A, C, and /), ropresentinp: 

 the three chromosome types) : simple trisomies, triplo-J. and triplo-Z> 

 and double trisomies, triplo-AC, triplo-AD and triplo-CZ). The ex- 

 pected triplo-(7 simple trisomic type has not been obtained, althontrh 

 each of the remaining five types was found repeatedly. Plate 57 

 illustrates the somatic chromosomes of the trisomic types, together 

 with the normal diploid chromosome complex. 



The trisomies are easily distinguished from the normal and 

 triploid plants. Besides their lower viability and slower growth, they 

 differ from diploids and triploids in the shape and color of the leaves 

 and in a number of other features. Different chromosomal types of 

 trisomies differ strikingly in their morphology, and can be readily 

 recognized without cytological investigation. 8ome of them approach 

 the triploid in fertility. A complete report of the investigations of 

 these trisomic types will be given in a later i)aper. 



The triploid plants of C. capillaris were finally crossed by Miss 

 Gerassimova with normal plants of various other Crepis species ; pri- 

 marily in the hope of determining the constitution of their gametes, 

 and also in order to test their crossability, which might differ from 

 that of normal plants. The majority of interspecific hybrids obtained 

 from the ai>pIication of the foreign pollen to the stigmas of the 

 the triploids proved upon examination to contain a diploid chromo- 

 some complex of C. capillaris together with a haploid chromosome 

 group of the other species used as the male i)arent ; moreover, viable 

 hybrids were obtained from crosses which had never been successful 

 when dii)loid C. capillaris plants were used for crossing. Thus a 

 hybrid between (\ capillaris and C. alpina was obtained, a cross which 

 had never been secured before. It has thus been shown that a triploid 

 l>lant undergoes interspecific hybridization more readily than a 

 <lipl(»i(l one. Finally, a hybrid i)lant was obtained which possessed 

 four haploid chromosome complexes of C capillaris and one of another 

 species {C. neglectn). This demonstrates that triploids may produce 

 viable tetraploid eggs in addition to haploid and diploid ones. These 

 l)olyploi(l hybrids of various kinds proved to be much more fertile 

 than the common diploid ones. 



For comparison with the conditions discovered in C. capillaris 

 the progenies of triploid plants of C. tectorum and C. dioscoridis were 

 studied. The behavior of these species proved to be entirely different 

 from (\ capillaris. The majority of the plants in llie progeny of 

 triploid ('. tccloruiii consisted of vai-ious trisomic types, and only a 



