450 Peirce. — Studies of Irritability in Plants. 
lasst sich leider nicht liber 2-3 Monate hinaus fortsetzen, weil die 
Pflanzchen auf einer kleinen Anheftungsstelle senkrecht auf dem Substrate 
aufsitzend naturgemass schlecht mit Wasser und mineralischen Nahrsalzen 
versorgt werden, und auch die Befestigung eine mangelhafte ist. Es lasst 
sich aber doch erweisen, dass die Dorsiventralitat auf dem Klinostaten 
nicht zu Stande kommt.’ 
This interesting experiment, in which the very marked and long- 
known dorsi-ventrality of M archantia failed to appear, suggested to me 
that possibly less imperfect plants, with the same radial structure, might 
be developed if, instead of beginning with multicellular and comparatively 
large reproductive bodies like gemmae, spores were used. Furthermore, 
gemmae are subject to the influence of light, mainly from one direction, 
during the course of their development on the surface of the thallus. 
Spores are also more or less illuminated, but only through the surrounding 
tissues of the sporophyte. Gemmae must develop at once, if at all, and 
there is no possibility of allowing the effect, if there be any, of light to pass 
off before they are sown. Spores can be kept for weeks or months in 
perfect darkness, and the following experiments will show that, in most 
cases at least, there is not the slightest evidence that they are permanently 
influenced by the light which filters through overlying tissues upon them. 
Although M archantia grows and fruits in the mountains not far from 
here, it is not easily accessible, and does not fruit at a season when one can 
conveniently sow the spores. That the spores may be kept as long 
as other Liverworts growing in dryer places I doubt. These other 
Liverworts — for example, Fimbriaria California ( Asterella ), and species 
of Anthoceros , &c. — and such Ferns as Gymnogramme triangularis, are 
abundant, and their spores may be collected in quantity, and sown when 
convenient. 
The great difficulty is in getting clinostats. A good clinostat is 
expensive, and few American laboratories can afford more than one or two 
good ones. Following Ganong’s directions 1 , I had ten eight- day clocks, 
of the alarm-clock shape but without alarms, cut down so that they ran at 
four times the speed, removed the hands, and put flat plates on the 
minute-hand spindles. These clocks therefore give cultures a revolution 
completed every fifteen minutes. In addition to these eight-day clocks, 
I had twelve one-day clocks ( £ dollar clocks ’), similarly fitted with plates 
carried on the minute-hand spindles. These clocks complete in one hour 
the revolution of a culture carried on the plate. By using clocks of these 
two speeds, I was led to believe that had Czapek used a faster clinostat he 
would have succeeded in getting, not folded, but solid cylindrical plants. 
I will discuss this point later, however. The mere mechanical labour of 
winding twelve clocks every day, and twenty-two clocks every other day 
1 Ganong, W. F., A laboratory course in Plant Physiology, pp. 120-1, New York, 1901. 
