The Influence of Light upon the Growtli of uni 
cellular Organs. 
By 
Sydney H. Vines, 
B. A., C'antab. 
The influence of light upon growth has been made of late years the 
subject of much careful investigation. The observations of Sachs 1 ) upon 
the growth of internodes, and those of I'hanti. - upon that of the leaves 
of Dicotyledonous plants, shew that the daily periodicity which is evident 
in the growth of those organs is. to be attribuled to the alternation of 
day and night. It appears that light exercises a retarding influence upon 
the process of growth, a conclusion w hich agrees with tbe inferences 
to be drawn from the phenomena of eliolation. 
ln order to study more closely the action of light upon growth, it 
will be well to lake the simplest possible form in which growth presents 
itself, and tliis is offered by unicellular plants or vegetablc organs. In 
this way many of the influences which modify the growth of more 
complex slructures, such for instance, as the various tensions existing 
belween cells when combined together to form a tissue, more especially 
when differentiation of lissues is taking place, are avoided, and au ap- 
proximale eslimate of the action of am one parlicular external force may 
be formed. That light exercises a povverfu! influence upon such organs is 
evident from the fact, that many ol thern (e. g. cells of Vaucheria and 
Mtella, byphae ot Fungi etc.) are positively heliotropic, and others, (e. z. 
lool-hairs of Marchantia) are negatively heliotropic. Recently Brhfeld 3 ) 
has called attention to the fact that the unicellular byphae of a Mould 
(Pilobolus microsporus) exhibits many of the appearances peculiar to etio- 
lation, when grown in the dark. He found that the byphae on which the 
sporangia would be developed under ordinär) circumstances, and which 
attain a height of about half an inch in the light, grew, in continued 
daikness, to a length of from eight to ten inches, and bore no sporangia. 
t) Arb. des bot. Inst, in Wttrzburg. Heft II. 1872. 
~ Alb - Bes bot. Inst, in Wttrzburg. Heft III. 1873. 
3) Bedeutung des Lichts für die Entwickelung der Pilze. Silzber. d. Gesellseh. 
naturforsch. Freunde zu Berlin, 17 . April 1377 . 
