248 CHARLES W. METZ 



und noch haiifiger von Funkia in vorgeriichten Prophasen gleich 

 grosse Chromosomen in Paaren nebeneinander liegen sehen 

 . . . . " ('05, p. 19). The pairing in these cases, as in 

 those of Montgomery, is seldom intimate, if one may judge 

 from the pubhshed figures, but there can be little question that 

 it is real.^ Somewhat later paired chromosomes were recorded 

 by Strasburger ('07) in root-tips of Pisum, by Sykes ('08) in 

 Hydrocharis, Lychnis and Bryonia,^ and by Overton ('09) in 

 root-tips of Calycanthus floridus, where the chromosomes are 

 said to be arranged in pairs not only during metaphase, but also 

 (as prochromosomes) in resting stages and prophases. In 

 Calycanthus, as in Pisum and some of the other cases, the size 

 difference between respective pairs is not noticeable, but the 

 pairing is very intimate, and if Overton's counts are correct 

 there can be no doubt as to the essential facts. ^" In the same 

 year Miiller ('09) described a pairing of chromosomes in somatic 

 metaphases of Yucca. The statements of Miiller were soon 

 challenged by Bonnet ('11) who maintained that since only 

 two sizes of chromosomes were present, and there were numerous 

 representatives of each, such associations as those described b}^ 

 Miiller were probably due merely to chance. In view of Mliller's 

 recent work ('12) however, in which he describes unmistakable 

 cases of pairing in other plants, it seems unlikely that he was 

 mislead by purely accidental phenomena in the previous case. 

 In 1910 Strasburger described further cases of chromosome 

 pairing in root-tips of Melandryum rubrum, Mercurialis annua, 

 and Cannabis sativa, in each of which different sized pairs were 

 evident, although the spatial association was not very conspicu- 

 ous. Stomps ('10, '11) during the same period found a com- 

 parable pairing in Spinacia, a plant possessing three large and 

 three small pairs of chromosomes. Similarly Nemec ('10) work- 



* Confusion has arisen in some cases by the application of the terms 'pairs,' 

 'paired chromosomes,' etc. to split, univalent chromosomes, and in other cases 

 by a difference of opinion between different investigators on the same material, 

 but those cited here are all based upon reasonably good evidence. 



^ Sykes at the same time confirmed the observations of Strasburger on Funkia 

 and Pisum. 



1" His conclusions have been disputed by von Schustow '13. 



