Pollen Mother -cells of Certain Plants . 45 
and by Shaw (’98), in Onoclea . Dublin (’05) reports a similar condition for 
the bryozoan Pedicellina . 
In testing Haecker’s (’02) hypothesis of the independence of the 
gonomeres, Strasburger (’05) finds that in Guignard’s (’91) figure of Lilium 
Martagon a double spirem stage appears, which may perhaps represent 
independent parental parts. He further examined the fertilized eggs of 
Iris and Triticum , without discovering any such separation of parental 
chromosomes. 
Although from my own studies upon the vegetative nuclei of plants 
showing prochromosomes I believe the parental elements remain distinct, 
I am thoroughly convinced that there is no such spacial separation of the 
parental nuclear parts as Haecker maintains, not even of the nucleoles. In my 
former studies I (’05) concluded that the ‘ Chromosomen der Urmutterzelle 
bleiben in der Pollenmutterzelle als Prochromosomen kenntlich ’ and ‘ Diese 
Prochromosomen zeigen sich parallel zueinander in Paaren angeordnet ’ and 
further ‘ Es ist sehr wahrscheinlich, dass die eine Halfte der prasynaptischen 
Chromosomen vaterlichen und die andere miitterlichen Ursprunges ist 
By an examination of Figs. 1-4 and 24, PI. VI, of my former work, which 
represent somatic cells, one may distinguish in many instances that the 
prochromosomes are arranged in pairs. Fig. 1, PL I, of the present study 
shows this condition distinctly, and I am very strongly convinced that the 
arrangement of the prochromosomes in somatic and young germ-cells is the 
same, that is, they are in parallel pairs. If this be so, there can be no 
constant independence of the entire pronuclei as Haecker maintains. Even 
though the parental parts may remain distinct for a while a final mixture 
occurs in such a manner, as I believe, that the homologous parental elements 
are brought side by side. 
I have very carefully examined root-tips of Calycanthus floridns and 
have observed that in the resting nuclei the prochromosomes are arranged 
in pairs. The prochromosomes in these root-tips are quite as large as the 
ordinary somatic chromosomes and have the same shape, and I think there 
can be no question whatever that they represent the greater portion of the 
chromosomes. In these root-tips I have also found the chromosomes 
associated in pairs just as Strasburger (’05) has described them for Fnnkia 
and Galtonia , in which plants he found the chromosomes of different sizes 
associated in homologous pairs during the prophases. Strasburger (’07) 
further reports that in the root-tips of Pismn y the chromosomes are arranged 
in pairs during the equatorial plate stages. 
The nucleus is, therefore, not only double in the sense that it contains 
two sets of parental chromosomes, but these chromosomes are so placed 
that there may be an interaction between homologous pairs. Allen (’05) 
points out that there is nothing in the evidence now at hand which 
absolutely negatives the possibility of an interaction between the two sets 
