340 BOTANICAL GAZETTE [NOVEMBER 
manner previously described are exposed to one-sided illumination, 
the holdfasts will appear always on the side away from the light. If 
spores germinate in darkness, the holdfast will be put out in all 
possible directions from different spores. This result I have repeat- 
edly obtained in Dictyota, Dictyopteris, and Laurentia, as well as 
in two species of Cystoseira, thus confirming and extending WINKLER'S 
(20) interesting experiments on C. barbata. The gelatine method 
which WINKLER used for part of his experiments is apparently more 
exact than mine, but what it gains in apparent exactness it loses in 
naturalness. The spores in a layer of sea-water not too thin (as it 
may be on a slide, especially if this is covered) quickly adhere to the 
surface of clean smooth glass, and if the dish remain undisturbed for 
several hours they are not likely to be dislodged by ordinary move 
ments afterwards. The use of gelatine, or of any other similar 
material even in dilute solution, such as WINKLER describes, is open 
to suspicion by reason of the facts reported in the foregoing part on 
fresh water algae, and also because of the results of BoRGE (3) already 
referred to, although WINKLER reports the germination as perfes 
normal. Naturally, for his gravitation experiments, 4 solid medium 
was necessary, but not for those on light. 
To escape the legitimate objection that the spores may behave 
differently in darkness and in light, I put upon the horizontal plate 
of a clinostat a dish in which Dictyopteris spores had escaped during 
twenty-four hours in darkness, covering the dish with a black ee 
of cardboard so that all the light came from the side. The plate 
the clinostat was also covered with dull black paper to avoid po 
reflection from below. The dish was therefore revolved in a ae 
tal plane and received light not only from the side, but on all frat 
successively. The clinostat was very simple — an alarm clock i 
which face and hands were removed, a sleeve carrying @ a a 
plate being soldered to the minute hand spindle. The pen 
therefore revolved once an hour. The result was that the Oe ae 
spores sent out holdfasts in all possible directions, some s es l until 
growing upwards, others downwards, the majority aout ee 
their increasing weight tipped the spores sufficiently to bring 
of the rhizoids into contact with the glass. 
+ oh 
It appears, then, that the side of the spore which is to - 
