204 
Francis Darwin. 
my point of view, it is clear that to the Narcissus flower-stalk, 
light is a signal that it has reached the open air, where 
alone its flower is capable of normal action. The same point of 
view is applicable to Coprinus : the stalk grows enormously, even 
as much as two feet in length, while the cap is either dwarfed or 
absent. Here again light is the signal that the cap has reached 
the open air where the spores can advantageously be scattered. 
It is instructive—and very much against the malnutrition 
theory, that the morphological peculiarities of etiolated plants 
appear where there is no malnutrition. According to Sachs the 
Hop is not affected by darkness, because it is “ naturally etiolated ” 
i.e. it is already throwing its whole energy into exaggerated longitu¬ 
dinal growth as an adaptation to the climbing habit. In the same 
way Noll 1 proposes to apply the term etiolation to the exaggerated 
growth of the petioles of certain floating leaves when the level of 
the water is artificially raised. 2 
To return to etiolation in the usual meaning of the word. 
Although I deny that the direct action of malnutrition explains 
the facts, yet as a stimulus it must be reckoned with. The condition 
of the plant which shows itself outwardly in elongation of internode 
and dwarfing of leaf is associated with darkness and with a certain 
degree of starvation. When the plant emerges from darkness, it 
is subject to two new conditions, viz .—illumination and a state of 
healthy nutrition due to assimilation. We have seen that the 
result normally due to two stimuli may be produced by one of 
them acting alone. Therefore we ought perhaps to find, if the 
plant is supplied with sufficient food, that etiolation will cease 
even in the dark. 
This has been shown by Jost to be the case (Pringsheim’s 
Jahib. XXVII, p. 444). A single leaf, nourished by the illuminated 
part of the plant, develops normally in complete darkness if freed 
from competition by the removal of all buds. Again Benecke 
(loc. cit.) shows that the gemmae of Lunularia , which normally 
refuse to germinate in darkness will do so if supplied with sugar 
in solution. 
On the other hand Vines found that some plants starved by 
1 Sitz. Nicderrhein. Ges. f. Natur -u. Heilkunde z. Bonn, 1901. 
* Benecke (Bot. Zcitimg, 1900). speaks of the etiolation of the 
rhizoids of Lunularia, the exaggerated longitudinal growth 
being here produced by starving them in the matter of 
nitrogen. 
