332 BOTANICAL GAZETTE [NOVEMBER 
illumination satisfactory. If the fruiting branches are put in the 
dishes late in the afternoon, enough spores will escape by nine o'clock 
next morning to justify removing the branches. In this way the 
age of the escaped spores may be confined within fairly narrow limits. 
If it were desirable to limit the age of the spores still more, as was 
sometimes the case, I made the cultures as soon as the fresh material 
was brought in, in the forenoon, and left them for four hours on the’ 
window shelf. In this time many spores escaped from good material, 
and I removed the fruiting branches. The dishes were left otherwise 
undisturbed for 22 or 24 hours after the cultures were made, in order 
to allow as many spores as possible to stick closely by their slimy 
coverings to the bottoms of the glass dishes. At the expiration of 
this time, the water in the dishes was carefully decanted, and fresh 
sea-water poured in. A considerable number of spores may wash 
out in this first change, but presumably they are the youngest, the 
ones last escaped from the fruiting branches, and there is the advantage 
in losing them that the material left in the dishes is still more nearly 
of the same age. Within these 24 hours the spores of Dictyoptens 
will have begun to germinate, putting out a short blunt process which 
is to form the holdfast, and having divided into two or three cells. - 
Cell-division, so far as the formation of a dividing wall is concernet 
does not seem always to precede the appearance of the process which 
is to become the holdfast; but there seems to a be slight difference 
in this regard between spores germinating under the ordinary 0% 
ditions of alternating daylight and darkness and those kept constantly 
in darkness. The latter generally form the division wall before 
putting out the process, but to this rule there are many exceptions 
In Dictyota and Cystoseira, however, the division wall is always 
plainly visible before the rhizoid appears. F 
The escape of th f Dictyopteris is much less abundant if 
pe of the spores of Dictyop ai 
the dishes are left in the dark than if they are normally light 
Thus, on November 11, at 12 o’clock, I put as nearly as ork 
equal quantities of fruiting Dictyopteris in eight dishes, two of en a 
I set on the window shelf and six in the dark. At 10 o'clock aie 
morning I counted the spores in all the dishes. There were 444 | 
elf.. In the #44 
I 359 219 ek 
75 spores in the dishes set on the window sh 
kept in the dark for these 22 hours there were 59, 134» 287, 
