STOUT AND 8U8A, CHROMOSOME IRREGULARITIES 3 



localities as Italy, France, Holland, Sweden, England and various sec- 

 tions in the United States have been grown together at The New York 

 Botanical Garden and have been carefully compared. These plants are 

 all indistinguishable. The studies to be reported in this paper relate 

 primarily to this vegetatively propagated and widely cultivated clon 

 of the single-flowered fulvous daylily. These plants will be referred 

 to as the "H. fulva clon Europa." 



At least twenty different papers have already been published which 

 deal with various aspects of the cytology of plants of this clon Europa. 

 In several of these papers it is reported that in these plants frequently 

 more than four pollen grains are formed from one pollen mother cell. 

 This fact was reported for this clon as early as 1882 by both Tangl and 

 Strasburger. Tangl (1882) concluded that these extra pollen grains 

 arise after the reduction divisions have been completed by the further 

 divisions of certain of the cells of the quartet. Strasburger, later in the 

 same year (1882), showed that irregularities appear in the first meiotic 

 division by the lagging of chromosomes, which then form small accessory 

 nuclei. Further and more extended studies were made by Juel (1897), 

 who found irregularities in the distribution of the chromosomes and in 

 the formation of the nuclei both in the first and the second meiotic 

 divisions. 



In general these papers present an excellent account of the irregularis 

 ties that result in the unequal distribution of chromosomes, in the lagging 

 of chromosomes and in the formation of micro pollen grains. These 

 earlier authors, however, did not settle the question as to what the nor- 

 mal and basic number of chromosomes is for plants of this clon, and 

 what is the range and the method of the variations in number beyond 

 and below that which is normal. 



Our studies show that the basic diploid chromosome number for 

 plants of the clon Europa is 12, but that the number may increase 

 both in somatic and in meiotic divisions, and that during micro-sporo- 

 genesis increases in the number of chromosomes and of chromatin units 

 are combined with irregularities in their distribution, with other ab- 

 normalities in nuclear division, and with the erratic organization of 

 nuclei until finally there is an abortion of spores that is almost complete. 



CHROMOSOME BEHAVIOR IN SOMATIC DIVISIONS 



The Basic or Normal Number of Chromosomes 



The normal number of chromosomes in the somatic cells of plants of 

 the Europa clon is 12. During the stages of nuclear division in somatic 



