Chromosomes in Pollen Mother-cells . 329 
less marked, and they are fewer than in Lilitim candidum (Figs. 36, 37). 
The spirem segments in part, at least, during the second contraction. The 
loops and the parallel straight or curved pieces of the thread often show 
a marked tendency to radiate from the entangled remainder (Fig. 37). 
This occurs simultaneously in a large majority of the nuclei in a given 
loculus, so that the picture obtained, even with low powers, is sufficiently 
characteristic to attract attention at a glance. When in the stage of 
Pigs. 36 and 37, which seems to be a regularly occurring step in this 
mitosis, the longitudinal fission, observable always at an earlier stage, 
cannot be recognized except in rare cases, and there can be no doubt 
but the loops and parallel pieces are due to an approximation of different 
parts of the spirem. This interpretation is borne out as the entangled 
mass of Fig. 37 is loosened sufficiently to show the individual chromosomes 
in their entirety. There is, however, a marked peculiarity shown in 
Tradescantia , which has been noted also by Miyake for this plant and by 
Strasburger for Galtonia . As soon as the chromosomes become more 
evenly distributed in the nuclear cavity, following the second contraction, 
some appear in the form of loops with closely applied sides ; others consist 
of paired rods, either straight or variously bent, and still others are 
connected into a chain, giving the impression that the spirem had not 
completely segmented, or that certain segments had become attached, 
end-to-end after cross segmentation (Figs. 38, 39). This end-to-end 
attachment of some of the chromosomes persists in some cases until 
metakinesis. In the stages of Figs. 38 and 39 and during the formation 
of the spindle (Fig. 40), the two members of the chromosomes may form 
short loops, with parallel parts more or less closely applied and either 
straight or twisted ; or the loops may be contracted into thick rings or links, 
open or almost entirely closed, or the two segments may adhere endwise. 
When the formation of these chromosomes is followed in detail, and 
when their structure is observed in the spindle during the anaphase (see 
Figs. 30-33, published by the writer in Bot. Gaz., xxxv, 1903), it is plainly 
evident that each is bivalent and that the two segments are really two 
chromosomes that were arranged end-to-end in the spirem. When we 
recall also that during the anaphase (Mottier, ’ 03 , Fig. 33) each of these 
segments is split lengthwise, it is highly probable that this is the fission 
observed in the spirem as it emerges from synapsis. 
Galtonia. A thorough study of all stages of Galtonia was not made, 
but so far as observation extended the process was found to agree more 
closely with that of Tradescantia and Podophyllum than with L ilium. 
This fact is now apparent from the figures of Strasburger (’ 04 ) and 
Miyake (’ 05 ). The interpretation of the formation of the chromosomes in 
this plant, published by Strasburger in the Sitzungsberichte der Koniglich 
Preussischen Akademie der Wissenschaften, is, therefore, the correct one. 
