Physiologcial Studies on Schistostega osmundncea. 27 



Summary. 



1) The optimum intensity of light for Schistostega osmim- 

 clacea is 0.02 — 0.002 (Bunsen's unit), the protonema thriving 

 well even in so feeble a light as 0.0008. The shoot, however, 

 never grows where light is 0.001 or below it. The relative 



" Lichtgenuss " is -. ^^^ and tlie optimum " Lichtgenuss " of the 



moss IS 



4 500 

 1 1 



50 200 • 



2) In a dark place, the protonema can live without produc- 

 ing, for seven months at least, a leafy shoot. In a place where 

 the intensity of light is over 0.1, the moss cannot live. 



3) The movement of chromatophores requires a considerable 

 length of time. When the protonema is placed in the light, the 

 chromatophores are scattered in a day, and when the direction of 

 light is changed, they all turn towards it in 7 — 10 days at a 

 temperature of 15^' — 25°C. 



4) The spherical cell of the protonema seems to enable the 

 moss to effect assimilation in a feeble light. 



5) The moss thrives better, and the movement of the chro- 

 matophore is faster in a blue and a violet light than in any other 

 visible light except a white light. 



6) The optimum temperature for the development of the 

 shoot is 16- — 25-C. The protonema will not die so long as the 

 temperature is above — 20.5"C., the shoot, however, dying at 

 -18-C. 



7) The optimum humidity of air is 90^— 100^. 



8) The protonema has a strong power of resisting desiccation. 



9) Elie and Émd^e Maechal's solution is the best cultural 

 medium for the moss. 



