Physiological Studit-s on Schistostega osmuncliicpa. JJ^ 



III. Influence of Light on the Growth of the Moss. 



Thanks to the researches of Servettaz (8), we now know 

 that for each sort of moss and at each stage of its development, 

 there is an optimum hght. If we wish to obtain a good result in 

 culture, we must device an arrangement which will allow the moss 

 to get as near an amount of light as the plant obtains naturally. 



Sclmtostega thrives well in a cave where the light is so 

 feeble that many other, common, species of moss could not live. 

 The classical researches of Noll and the recent studies of Senx, 

 show that the cell of the protonema, being lens-shaped, can effect 

 assimilation in a feeble light quite as well as other species do in 

 much brighter places. 



1. Optimum Intensity of Light and optimum " Lichtgenuss." — 

 In my present study I first estimated the optimum intensity of the 

 light and the optimum " Lichtgenuss " at Yutanaka. Results of 

 which are given in Table I. 



At the farther end of the cave, tlie intensity of light was 

 between 0.0013 and 0.0111 (Bunsen's unit), while near the entrance, 

 it was between 0.01 and 0.09. Outside the cave, it was between 

 0.17 and 1. 



In the cave, the shoots grow most abundantly near the 

 entrance, while the protonemata thrive best at the farther end. 

 It seems, therefore, that the optimum intensity of light for the 

 development of the protonema- is between 0.008 and 0.002, and 

 that for the shoot is somew^hat below 0.09. It wall also be seen 

 that the optimum intensity of light for tlie moss is between 0.02 

 and 0.002. 



The relative " Lichtgenus " of the moss at about 1 m. from 

 the entrance of the cave is observed to be: L — ^^— -^^ and at 



