212 MR. 8. LE M. MOORE’S STUDIES 
in until some time afterwards. This is by no means an excep- 
tional case. Elodea, Vallisneria, Ceratophyllum, Callitriche, and, 
to a considerable extent, Lemna trisulca show the same peculi- 
arity. Thus, positively apostrophized Elodea-grains move into 
epistrophe within forty-eight hours of removal to the dark, and 
it is now impossible to detect any difference in the distribution 
of darkling and illuminated grains; and the same may be said, 
except for variations as to time, for all the rest. Moreover 
Pteris cretica and P. serrulata, Oxalis Acetosella, and Saxifraga 
granulata resemble the above-mentioned aquatic types. On the 
other hand, the positively apostrophized chlorophyll of Funaria 
hygrometrica remains in apostrophe on exposure to darkness, as 
does that of Urtica urens stipules, and of Centranthus ruber and 
Eschscholtzia californica mesophyll. 
The results obtained under this head may thus be summed up :— 
(i.) The epistrophized grains of sun-loving plants (both Pha- 
nerogams and, so far as experiment has yet gone, Cryptogams 
also) are negatively apostrophized after a few hours in darkness. 
Cii.) Negative apostrophe is very slow in making its appearance 
in aquatic types (Lemna trisulca being a partial exception), and 
likewise in shade-lovers, such as fern- prothallia, Pteris, Oxalis, 
and Saxifraga granulata*. 
(iii.) Negative apostrophe can be induced in sun-loving plants 
in low light. 
(iv.) The effect of continued darkness upon grains already 
apostrophized is to drive them into masses in the corners, or, 
more rarely, upon the side-walls of the cell. This is much more 
quickly brought about in sun-loving than in aquatic types. More- 
over it may also occur in palisade-tissue. 
(v.) Still longer exposure to darkness may cause many if not all 
of the grains to come out on to the free (superficial) walls, where 
they may remain distributed with fair uniformity or collected 
into larger or smaller masses. 
(vi.) Positively apostrophized grains of sun-lovers remain in 
apostrophe on removal to the dark ; those of aquatics and shade- 
lovers are to a greater or less extent epistrophised by this 
treatment. 
The Epistrophic Interval. 
If, on a dull day in late summer or autumn, a leaf be taken 
* With respect to this last see p. 219. 
