368 MR. 8. LE M. MOORE’S STUDIES 
during the past summer in strong sunlight left me no alternative 
but to decide that Stahl had misread his text zn toto; but a 
resurvey of the ground in October has convinced me that he is 
correct, but only so far as weak sunlight is concerned, under 
which circumstances, on several occasions, I saw the broadside 
plate slowly turn over and take up its position along the axis 
of the cell, the only difference observable between this movement 
and that in diffused light being the longer time required—from 
20 minutes to half an hour as against 10 minutes; and the only 
effect of continued insolation was to cause the appearance of 
curves in the plate. In strong sunlight*, however, the turning 
movement is in abeyance, as reference to figs. 20 a-e will show. 
The first of these (fig. 20a) indicates the approach of either half 
of the plate to a side-wall; but as the relation is to opposite sides, 
a curved figure ensues, the central part of which remains in its 
original position f. Fig. 20 5 shows a plate of which both halves 
have been similarly affected, in consequence of which it: has 
moored itself to one ofthe side-walls, where, however, it still lies 
face up, its position before insolation: at a further stage the 
plate has turned round upon the side-wall, thus completing its 
apostrophe (fig. 20c). The effects of the sun may sometimes be 
more violent than this ; for instead of one half of the plate being 
forced to one side of the cell and the other to the opposite wall, 
this difference may manifest itself in the same half, the upshot of 
which is a sigmoid figure (fig. 215); or while the centre of the 
plate is urged to one wall, the two ends make for the other, 
whereby the form of a wide saddle is produced (fig. 21a). In 
all this there is nothing but what might be expected @ priori; 
given a long and wide ehloroplast and an alternative position in 
the cell; it finds its analogue in the streaming movements over 
the illuminated (superficial) walls of the cells of insolated Zlodea- 
leaves, movements which may even continue for a little time 
after rotation has declared itself. These figures, which take from 
& half to one hour to produce, are not pathological; for they are 
abolished after some time in diffused light, likewise within twenty- 
four hours in darkness, and the re-formed plate is unimpaired, 88 
is proved by its capacity to swing round just as before insolation. 
* In autumn as well as in summer. 
+ Compare this with fig. 7c, which shows the same thing in Selaginella 
Martensii. 
Li 
