66 DUDLEY MEMORIAL VOLUME 



each cup, and screwed to the shelves. So long as the diameter of the bore 

 of the cups remains uniform and the wear of the axis corresponds, the motion 

 of the turn-tables should be uniform. The turn-tables themselves are made 

 of a light alloy, Alzine, which sometimes appears to be too brittle; but if 

 not, teeth of great uniformity may be cut in the edges of the turn-tables. 

 When the regular teeth of adjacent turn-tables are so set that they do not 

 bind or allow too much play, with the inevitable contraction and expansion 

 of the shelves and frame in the changing temperatures and humidities of a 

 laboratory, the clock-work drives them with great regularity. Indeed, next 

 to the very desirable feature of carrying many cultures at once on this multi- 

 ple clinostat, the regularity of revolution is its most valuable feature. 



It may not be necessary to add that the multiple clinostat now in my 

 laboratory, and thus briefly described, is the product of the experiments, fail- 

 ures and successes, of the last six years. Each improvement has been the 

 fruit of failure. Some of these failures have been very disheartening, for 

 one does not like to lose or to vitiate the accumulated result of six or eight 

 months of work by the clock-work or any set of turn-tables coming to a stand- 

 still for an hour. 



EXPERIMENTAL WORK. 



Only one or two of the questions suggested by my previous work and 

 left unanswered in that' paper will be considered in this. The plants which 

 I have experimented upon have been the prothalli of Pteris aquilina and Gym- 

 nogramme triangularis, grown from the spore on tile; plants of Porella Bo- 

 landeri, a foliose liverwort which I brought into the laboratory from rocks 

 and tree-trunks near by and cultivated on the tile in crystallizing dishes; 

 plants of Fimbriaria (Asterella) Calif ornica, also grown from the spore; 

 Anthoceros fusiformis, grown from the spore and used simply as a check, for 

 the results on turn-table and shelf were the same as previously reported; and 

 plants of white mustard and of wheat, raised in two-inch flower pots in good 

 soil from the seed. The results are in the main similar, and I shall discuss 

 them all together after separately describing the experiments on the different 

 sorts of plants. 



Porella Bolanderi (Aust.) Pearson. 



On November 14, 1907, I collected plants of Porella Bolanderi growing 

 on rocks and tree-trunks about a half mile from this University. The plants 

 were dry and dormant. I sorted these, after moistening with sterilized water, 

 and selecting clean branches about a centimeter long, placed these upon 



