282 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN | VOL. 10 



This second type of chromosomal deviation is a type of polyploid in which 

 the chromosome size regularly decreases when the number of chromosomes in- 

 crease. When the chromosome number is doubled from 12 to 24, the size of the 

 chromosome is reduced to about half that of the standard length (AL-type). 

 These smaller chromosomes are referred to as the BL-type, and are about 0.6 /x 

 long. Some species also have 48 chromosomes that are about half the size of the 

 BL-type ; these are referred to as the CL-type. The chromosomes of the CL-type 

 are almost spherical at metaphase, and average about 0.4 /x in length. This type 

 of polyploidy is referred to as endo-nuclear polyploidy by Nordenskiold (1951). 



The majority of the species studied have essentially the same chromosome size 

 throughout the cell. However, in some species distinct differences in chromosome 

 size are found, a condition often connected with an aneuploid chromosome num- 

 ber. This is the third type of chromosome deviation and results in the replace- 

 ment of one AL-type chromosome (1.1 /x long) with two chromosomes of the 

 BL-type (0.6 /x long) and two chromosomes of the CL-type (0.4 fx long) replac- 

 ing one BL-type (1AL = 2BL = 4CL) . This type of chromosome deviation has 

 been interpreted as half completed endo-nuclear polyploid. An important fea- 

 ture of endo-nuclear polyploidy is that though the chromosome number is dou- 

 bled, the DNA value remains the same (chromosome ratio 2:1; DNA ratio 1:1). 

 In contrast, in a normal polyploid series the chromosome number as well as the 

 DNA value is doubled (chromosome ratio 2:1; DNA ratio 2:1). 



Present cytological information indicates that the subgenus Anthelaea is the 

 most primitive. The simplest chromosome pattern in the genus is found in this 

 group. In this subgenus Buchenau (1906) recognized two distinct morphological 

 groups, and Nordenskiold (1951) found that the cytology of these two groups 

 also differs. In the first group all of the species studied have a diploid number 

 of 12 and the chromosomes are of the AL-type, while in the second, different 

 chromosome patterns have been reported. These variations are the result of 

 endo-nuclear polyploidy and no aneuploidy or normal polyploidy has been found. 

 In the subgenus Pterodes only seven species have been studied cytologically, and 

 no number below 24 has been found. In this subgenus a normal polyploid series 

 does not occur, but endo-nuclear polyploidy as well as aneuploidy exists. No AL- 

 type chromosomes are present and in most species the chromosome numbers re- 

 ported are the same for anyone species. The subgenus Luzala, which is the larg- 

 est in the genus, is the only one in which all three forms of chromosome variation 

 exists. At present, the only members of the group that have been studied cyto- 

 logically are the species from the Northern Hemisphere. The numerous species 

 of South America and New Zealand have not been studied. 



Geographic distribution is often useful in ascertaining the center of origin. 

 In Luzula, this information, correlated with cytological and morphological data, 

 is useful in determining phylogenetic relationships. The subgenus Anthelaea is 

 largely restricted to Central Asia and Europe, with a few species extending into 

 North America. In the subgenus Pterodes, only three species are found in Europe, 

 but two of these (Luzula forsteri and L. luzulina) have the lowest chromosome 

 number found in this group. The remaining species have a higher chromoso],-:- 

 number, and are distributed throughout the Northern Hemisphere, with one, 

 L. johnstonii, in Africa. In contrast, the large subgenus Luzula, has a world 

 wide distribution, but has many diploid species in Europe and Central Asia. 

 This suggests that the subgenus Anthelaea is the most primitive, and that it 

 originated in Central Asia or Europe. From this complex the subgenera Pterodes 

 and Luzula then developed independently. 



