Pollen Mo ther -cells of Li Hum canadense. 209 
tion between the ends so in contact. This is especially true in triple- 
stained sections; but in material carefully stained with iron haematoxylin, 
in which the colour is washed out of everything except chromosomes and 
nucleoles, it is possible in the majority of cases to determine that the ends 
of the daughter chromosomes, even though in contact, are really separate. 
In some cases it is impossible to distinguish the separate ends, and there 
appears, at least, to be a more or less complete fusion. The chromosomes 
represented in Figs. 43 and 46 show such an apparent fusion, and in those 
shown in Figs. 36, 38, and 42 the fusion is less complete. In Fig. 42 the 
daughter chromosomes are in close contact at both ends, and it may be, 
though from their position it is impossible to determine, that a similar 
partial fusion has occurred at both ends. The daughter chromosomes in 
Fig. 52 are closely in contact at one end, but there is no evidence of 
fusion. 
Whether this fusion at one or both ends be real or apparent, it is 
certain that its occurrence in Liliuni canadense is much less common than 
has been described for many species of this and other genera. The 
phenomenon is not noticeably more frequent at any one stage than at 
any other, although I have never found it before a certain amount of 
shortening has occurred ; and at any period the great majority of the 
chromosomes are plainly two-parted throughout their length. 
At the time of segmentation the halves of each mother chromosome are 
several times twisted about each other (Fig. 33) ; they are closely appressed 
in most parts, and there is seldom any considerable divergence at any 
point. As the process of shortening and thickening proceeds, its natural 
result is a gradual lessening of the number of twists. The course of un- 
twisting may be followed in Figs. 33, 34, 37, 38 and 41. A common effect 
of this untwisting is a lessening of the closeness of contact between the 
daughter chromosomes, and a divergence from each other at one or both 
ends or in the middle. Some retain a considerable twist in the mature 
form, e. g. Fig. 30. Perhaps the commonest case is the retention of a 
quarter- or half-twist in the middle portion, with the ends more or less 
diverging (Figs. 35, 40, 45, 47, 51). Occasionally the twist is entirely lost, 
and the daughter chromosomes remain in contact only at the centre of 
each ; thus such a peculiar form may arise as is shown in Fig. 44, where 
each daughter chromosome is bent into a U, the two U’s lying in 
planes perpendicular to each other. In some cases the daughter chromo- 
somes lie close to each other and approximately parallel, with little or no 
twisting ; instances of this sort are shown in Figs. 36, 42 and 52. They 
may remain in contact at one end, diverging widely at the other (Fig. 43) ; 
or they may be in contact at or near both ends, with the centres diverging 
(Figs. 49, 53). In these various ways, as a result of the untwisting of the 
daughter chromosomes and of their adhesion or divergence at various 
