374. Mrs Arber, On Root Development in Stratiotes aloides L. 
true that Miss Kemp* has shown that nuclei of abnormal shape 
may be produced experimentally by poisoning young roots, but the 
results are far from being so uniform and regular as those just 
described for Stratiotes. The plants in which I have observed the 
lobing of the nuclei were obtained from two different localities 
in three different years; it is scarcely likely that identical toxic 
effects would occur independently in three sets of material, which, 
in each case, appeared to be quite healthy. It should also be 
remembered that the young adventitious roots, in which the 
multinucleate cells and lobed nuclei were observed, were still more 
or less completely embedded in the stem tissues of the parent, 
and thus presumably protected to some extent from adverse | 
external conditions. 
The presence, in the young roots of Stratiotes, of nuclei 
bilobed in various degrees, and also of certain cells containing 
more than one nucleus, seems to indicate that the lobing cul- 
minates in complete bisection. I believe that this is the case, 
and that amitosis takes place; I am inclined to go further and 
to think that these amitoses may be followed directly, or after 
an interval, by cell-wall formation, and that amitosis thus actually 
i I 9 EL OE 
plays a part, supplementary to karyokinesis, in the development — 
of the embryonic root of Stratiotest+. It is naturally almost im- 
possible to prove that cell-walls are formed in connexion with 
these direct nuclear divisions, but I have more than once seen 
appearances decidedly suggestive of such an occurrence. The © 
fact also that, in the young roots, bilobed nuclei are much more 
frequent than multinucleate cells, and, again, that the mature 
roots are not characterised either by bilobed nuclei, or by a number ~ 
of multinucleate cells corresponding with the numerous bilobed 
nuclei seen in the younger stages, is difficult to explain unless » 
wall formation has occurred between daughter nuclei formed by — 
direct division, for there is no evidence that any nuclei are — 
resorbed. 
It is, in the nature of the case, very difficult, if not impossible, 
to offer a convincing proof of the contention that amitosis plays 
an active part in the growth of the young roots of Stratotes, | 
and I have hence allowed more than four years to elapse since ~ 
I made my first observations on the subject, as I felt reluctant 
to put forward such a heretical opinion in any haste. I am aware — 
that cytologists may prefer to regard the occurrence of these lobed 
nuclei as a mere meaningless anomaly. However, each time that — 
* Kemp, H. P., ‘‘On the Question of the Occurrence of ‘ Heterotypical Re- 
duction’ in Somatic Cells,” Ann. Bot., vol. xxiv. p. 775, 1910. 
+ I have observed a nucleus dividing by karyokinesis in a section of a root-stele 
in which lobed nuclei also occurred. 
