376 Mrs Arber, On Root Development in Stratiotes aloides LT. 
recorded. The tentative suggestion which I wish to bring forward 
is that amitosis has been adopted in the young roots of Stratiotes 
as a means of very rapid nuclear multiplication*, which supple- 
ments karyokinesis and thus renders possible a period of extremely 
rapid growth. It may, further, in this case be associated with the 
somewhat peculiar conditions under which the young roots de- 
velope. Owing to the corm-like form of the short main axis of the 
plant, the adventitious roots arise at some little depth from the 
surface and have to force their way for an appreciable distance 
through solid cortical tissue (P]. VIII, Fig. 1), which must act as a 
temporary check upon their expansion. Luxuriant growth-activity 
is a well known characteristic of water plants, but under the con- 
fined circumstances in which the adventitious roots of Stratiotes 
aloides are initiated, this energy of development does not seem 
to find an adequate outlet in actual increase in size. It is perhaps 
conceivable that it may be temporarily diverted into other channels, 
and find its expression in amitosis. 
IV. On the Significance of Amutosis. 
Amitosis, or direct nuclear division, seems to be generally 
regarded at the present time as a degeneration process, at least 
where it occurs among the higher plants. This, which we may 
describe as the orthodox view, has been championed by Stras- 
burgert, who held that karyokinesis and “ fragmentation” were 
two entirely different processes, the former taking place under the 
influence of the surrounding protoplasm, and the latter occurring 
when the influence of the protoplasm was on the wane, so that the 
nucleus “seinen eigenen Gestaltungstrieben folgen kann{.” He 
stated that he knew no case in which cell division followed 
amitosis, which he regarded as a phenomenon of senility. The 
same view has been taken by Zimmermann§ and other writers. 
Johow||, on the contrary, who was the first to point out that 
amitosis is a wide-spread phenomenon among Monocotyledons, 
protests against the use of the word “fragmentation ” on account 
of its pathological implication. It was Johow who drew attention 
to the pith cells of Tradescantia which are now so widely used for 
teaching purposes to illustrate amitotic nuclear division, and he 
* Cf. Shibata’s work on amitosis in mycorhizal tubercles, referred to in the next 
section of the present paper. ; 
+ Strasburger, E., ‘‘Kinige Bemerkungen itiber vielkernige Zellen und iiber die 
Embryogenie von Lupinus,” Bot. Zeit. 1880, p. 845 ete. (See also Ibid., ‘‘ Die 
Ontogenie der Zelle seit 1875,” Progressus Rei Bot., Bd. 1. Heft 1., p. 22 ete., 1907.) 
+ Lc. p. 852. 
§ Zimmermann, A., ‘‘Die Morphologie und Physiologie des pflanzlichen Zell- 
kernes,” p. 49, Jena, 1896. 
|| Johow, F., ‘‘ Untersuchungen iiber die Zellkerne in den Secretbehaltern und 
Parenchymzellen der héheren Monocotylen,” Inaug. Dissert., Bonn, 1880. 
