Chromosomes in Pollen Mother-cells. 317 
Figs. 19 and 20 that were stained with the triple stain, the linin portion is 
colourless, while the chromatin granules remain blue. This means, of course, 
that in the process of differential staining the safranin is removed from the 
linin and chromomeres almost completely, and that the latter retain 
the violet stain with greater avidity. The condition of the nucleus as 
shown in Fig. 19 has been described by Farmer and Moore (’ 05 , p. 508) 
for they state that ‘ the definite spirem thread can be distinguished very 
clearly at an early period in karyokinetic activity, certainly long before 
the spore mother-cells dissolve their union with each other. It forms 
a colourless thread, at first infiltrated with chromatin throughout, but the 
latter soon collects into serial beads so as to give rise to the well-known 
alternation of stainable (chromatin) and non-staining (linin) disks.’ 
Farmer and Shove (’ 05 ) figure a similar presynaptic structure in 
Trcidescantia virginica. A spirem of a single row of granules has been 
described by Schafifner (’ 97 , ’ 06 ) as representing the presynaptic condition 
in Lilium philadelphicum and L. tigrinum. In fact this has been the 
interpretation of most cytologists in former years. Allen (’ 05 ), on the 
contrary, does not mention any such stage as the writer’s Fig. 19, as 
occurring prior to synapsis. 
From what has been described in preceding paragraphs, the possibility 
is not excluded that the chromatin may not always be in the same state of 
reticulation, or distribution within the linin framework, prior to the con- 
traction into the dense mass. In Figs. 22 and 23, which do not seem in 
any way to represent artefacts, the chromatin exists in the form of lumps or 
masses, while in other cases (Figs. 19, 20, 21), there has taken place 
a much finer reticulation of the chromatin, so that the granules are much 
more numerous, of uniform size, and arranged in a single row within the 
linin reticulum. Whether we have in Figs. 19 and 20 a continuous thread, 
or thread and network combined, cannot be stated with absolute surety ; 
but it is certain that a large part of the structure is a thread (Fig. 20) with 
only one row of granules, or we may say chromomeres. When we 
compare Fig. 18 with Fig. 19, it seems reasonable that the structure of 
Fig. 19 has been derived directly from that in Fig. 18. Anthers, showing 
the structure of Figs. 19, 20, 21, seemed to be in about the same stage 
of growth as those in which Figs. 22 and 23 were found, especially when 
one remembers that Figs. 16 and 18 were drawn from the same section. 
In all cases the pollen mother-cells, up to the time of synapsis, are 
contiguous throughout, forming a continuous tissue connexion without any 
intercellular spaces at the corners of the cells. 
Whether the disposition of the chromatin, as described and figured for 
the plants in question, is due in any respect to the action of fixing fluids or 
not — this seems certain, namely, that, before or during synapsis, the 
chromatin becomes resolved into relatively small granules which do not 
