762 
GENERAL CONDITIONS OF PLANT-LIFE. 
observation shows that it is not the rays absorbed by the green colouring matter that 
perform this work either in the solution or in the living plant ^ 
The Relation of Cell-di-vision to Light has, as I have already explained, been completely 
misunderstood by Famintzin. In my paper * On the influence of daylight on the 
formation and unfolding of various organs of plants' (Bot. Zeit. 1863, Supplement) 
I described in detail a long series of phenomena which show that the fresh formation 
of parts connected with cell-division is in general independent of light as long as 
there is a supply of reserve food-material to support growth. The main results were 
again collected in my 'Handbook of Experimental Physiology,' p. 31, referring also 
to that paper. Notwithstanding this, Famintzin ^ commences his paper quoted above 
(three years later than one, and five than the other of my works) with the words : 
'The action of light on cell-division has not yet been carefully examined by any 
one. All that I have been able to find on this subject is limited to a remark of 
A. Braun's on Spirogyra and a statement of Sachs relating to cell-division in general.' 
He then quotes a passage from Braun cited also by me, and continues ' Basing his 
remarks on these statements, Sachs expresses himself as follows,' and then quotes 
some passages from my Handbook, p. 31, no reference being made to the earlier 
paper or its conclusions. He then maintains that his own observations lead to entirely 
different results ; but it is easy to show that they rather lead to the same as mine. 
At the end of his memoir (p. 28) he says: — 'The cell-division of Spirogyra is not 
prevented by light, as has hitherto been supposed, but on the contrary is promoted 
by it' (which is incorrect). According to Famintzin's observations, this acceleration of 
cell-division by light depends on the fact that light induces the assimilation of food- 
material ; which is obviously a different question from that argued by me and opposed 
by him ; since, presupposing the presence of a supply of food-material, I only argued 
the question whether light exerts any influence on the physical fact of cell-division. 
' The cell-division of Spirogyra,^ continues Famintzin, ' has been proved to be de- 
pendent on light to the same extent as the formation of starch ; but the relationship 
in the former case diff'ers from that in the latter in the following respect : — the formation 
of starch is induced by a very brief exposure to light (aboiit half an hour) and requires 
that its action be direct; starch is formed only under the influence of light; in its 
absence the formation at once ceases. Cell-division, on the other hand, is induced 
only after light has acted for some hours ; it then commences in the cells whether 
these are exposed to light for a longer time or are removed into the dark.' This 
shows therefore that when food-materials are formed cell-division takes place in the 
light as in the dark ; a fact which I had proved five years before by a greater number 
of observations. 
Better in more than one respect is Batalin's treatise ' On the action of light on 
the development of leaves' (1871)^ Starting from the facts discovered by himself 
and by Kraus that cells have the same size in small etiolated leaves as in large 
leaves of the same species grown in light, he concludes with justice that the number 
of cells is larger in the normal than in the etiolated leaf, and that the size of leaves 
is proportional to the number of cells in them. But from this he draws the following 
erroneous conclusion : — ' The leaf grows so long as it produces new cells ; and the 
growth of the leaf does not depend on the increase in size of the cells.' It should 
rather be, — ' The growth of the leaf depends firstly and directly solely on the increase 
in size of the cells, and is proportional to this ; but the cells, when they have grown 
larger, divide so that they are actually of about the same size in the small etiolated 
as in the large green leaf.' He continues : — ' Leaves do not grow in the dark because 
^ Gerland (/. c. p. 609) has also arrived at a similar conclusion. 
^ Famintzin, Melanges phys. et chim., Petersbourg 1 86.8, vol. VII, On the action of light on 
the cell-division of Spirogyra. 
2 Balalin, Bot. Zeit. 187 1, p. 670. 
