1929] Navashin: Triploidy in Crepis 393 



(M. Navashin, 1927). At any rate, there is no doubt that the 

 unbalanced conditions of the nucleus in some way stimulate chromo- 

 some alteration. Although the viability of individuals possessing 

 fragmented chromosomes is greatly reduced, there is still some prob- 

 ability that fragmentation of some sort may take part in species 

 formation. In this connection one may refer especially to C. parvi- 

 flora, which possesses an extremely short satellited chromosome and 

 another longer one, both suggesting in a way the products of frag- 

 mentation of the usual satellited chromosomes of C. capilJaris or 

 C. tectorum. It is of interest to note that the same process of frag- 

 menation has also been reported in progenies of triploid tomatoes by 

 J. W. Lesley {loc. cit.). 



SUMMARY 



1. Triploid individuals have been found in many populations of 

 Crepis capilJaris, C. tectorum, and C. clioscoridis, in some instances 

 in proportions up to one per cent of the total number of plants. Such 

 a high degree of occurrence cannot fail to influence the biological 

 behavior of the species involved. 



2. Triploid individuals differ morphologically from normal ones 

 only in quantitative features; viz., in enlarged general dimensions 

 and organs, in enlarged cells and cell organs, in increased size of 

 fruits, etc. 



3. The tempo of development of the triploid plants is significantly 

 delayed, although the viability is not perceptibly reduced. 



4. The fertility of triploids is greatly reduced ; triploid plants of 

 C. capHlaris produce on the average only about 21.8 per cent of good 

 seeds, because of failure of the majority of ovules to function. Simi- 

 larly the majority of pollen grains are aborted. 



5. Cytological investigations of triploids has shown that their 

 chromosomes do not differ in any way from those of diploids except 

 they are present in triple number. 



6. The first and second generations obtained from the original 

 triploid C. capilJaris plant have been investigated cytologically, the 

 total number of plants examined exceeding 1000. In C. capillaris 

 92.7 per cent of all the progeny of triploids consists of diploids (63.9 

 per cent) and triploids (28.8 per cent) ; the remaining 7.3 per cent 



