SCIENTIFIC SUMMARY. 
89 
enclosed and brougM under cultivation, tlie species composing its original 
flora become weeds in tbe new fields. 
Plants within Plants. — Tbe discovery which M. Trecul some time since 
announced, of the existence of minute vegetable organisms within the starch- 
cells of Helianthiis tuherosus, and to which he gave the name of Amylo- 
bacteria, has been regarded by him as a decided proof of the spontaneous 
generation of plants. Thus, although the doctrine of heterogeny has lost its 
main advocate by the recent recantation of M. A1 Donne, it has found 
a new and powerful ally in the person of M. Trecul, one of the most eminent 
botanists in Trance. M. Trecul defines vegetable heterogeny to be ‘^a 
natural operation by which life, when about to abandon an organised body, 
concentrates its action in some of the particles of this body, and converts 
them into beings quite distinct from those they proceeded from.” We do 
not admit the logical force of M. Trecul’s argument so long as it is admitted 
by physiologists as proven that vegetable forms of the lowest type may enter 
the tissues of animals. There is no more wonder in the fact of a cholera- 
fungus in the blood of man than in an Amylobacterium in the starch-cell of 
a Helianthiis tuherosus. 
Movements of Minute Green Organisms. — In a most interesting paper on 
the movements of microscopical plants, which is translated in the last number 
(October) of the Quarterly Journal of Microscopical Science, Professor F. 
Cohn gives us the result of his careful observations of the peculiar rotatory 
motion of the lower vegetable organisms and of the relation of this motion 
to the influence of light. The paper contains so many important details, 
that we must refer our readers to it for fuller information. We may 
mention, however, that Professor Cohn, who shows that light causes these 
microphytes to move in a definite direction, gives this explanation of the 
phenomenon : — “ If we consider these facts concerning the movements of 
organisms which possess a green and a colourless half in connection with the 
property^ of chloroph)^! to effect, through the agency of actinic rays, certain 
chemical actions — in particular the decomposition of carbonic acid and the 
separation of oxygen — it appears probable that all these phenomena of move- 
ment, as far as concerns their direction being caused by light, depend upon 
the chemical activity of these bodies. We can, in fact, imitate, by pure 
chemical processes, with the help of what may be called an artificial Euglena 
(namely, a fusiform fragment of chalk, half of which is covered vvith a 
resinous cement, and which is placed in diluted sulphuric acid), many of the 
phenomena recorded above. The splinter of chalk develops oxygen on its 
uncovered half, and is thereby projected by the backward impulse in the 
direction of the covered end, and is caused to rotate.” 
OHEMISTKY. 
The Atmosphere of the Underground Railway. — Most of our readers are 
aware that the evidence of the Chemists, Messrs. Letheby and Rodgers, who 
examined the air of the Underground Railway, led tlie jury to return a ver- 
dict to the effect that the atmosphere of the tunnels was not dangerous to 
health. In this verdict we cannot agree, however legally accurate it may 
