with special reference to the occurrence of Amitosis, etc. 375 
TL have returned to the subject, my original impressions have been 
strengthened, and I think it is perhaps now advisable to publish 
a preliminary account of my conclusions in the hope that they 
may receive confirmation or correction from other workers. 
It has been suggested to me that, even if the facts are as I 
suppose, it is not necessary to regard this form of nuclear division 
as genuine amitosis, but that it may be interpreted as a masked 
form of karyokinesis, due to incomplete separation of the chromo- 
somes. I think this view is somewhat strained, and would be 
difficult to accept in any case, but in regard to Stratrotes it is 
certainly untenable. It could only hold good if the chromosomes 
were few and large, whereas in this plant they are small and 
numerous. This point can readily be observed in the case of the 
nuclei dividing by normal karyokinesis, which are frequently to 
be found in the root-tips. 
The remarkable difference in size between the ordinary vege- 
tative nuclei and those of the young root-hair cells and vessels 
(cf. Pl. VIII, Figs. 3 and 4, and Pl. 1X, Fig. 6) suggests that the 
nuclei of Stratiotes aloides are unusually plastic,—thus partaking 
in the general plasticity which is so marked a feature of water 
plants, and which has probably been a primary factor in de- 
termining the possibility of any particular group or species 
adopting the aquatic habit. Assuming that amitosis does actu- 
ally occur in the young roots, we may, I think, interpret it as 
a special adaptation to the unusual requirements of the species. 
It is well known that the young plants of the Water Soldier, 
produced at the ends of stolons arising from the parent rosette, 
pass the winter at the bottom of the water and rise to the surface 
in the spring or early summer. Roots are not needed so long as 
the plant is submerged, but, when it rises to begin its floating 
phase, a quantity of remarkably long roots are produced with great 
rapidity. The use of these very long roots is probably to maintain 
the equilibrium of the rosette. 1 noticed, in the case of two 
plants which I’cultivated, that the loss of their roots, through the 
depredations of water-snails, deprived them of all power of keeping 
upright in the water, so that they were generally to be found 
floating on their sides. The young plant rises to the surface in 
the form of a rosette, not, as in the case of the related Hydrocharis, 
in the form of a compact winter-bud; being, as it were, full- 
fledged, it requires its roots at once. That the growth of the 
roots is unusually rapid is proved by some measurements which 
Mr Aveling Green has kindly taken for me. He kept records, 
during part of July and August 1911, of the growth of eleven 
roots belonging to three plants of Stratiotes alozdes cultivated in 
a pond in his garden, and several times observed an increase of 
over 2 inches in 24 hours; on one occasion, even 2% inches was 
