16 Art. 5— Y. Todii: 



shoots were bent towards the Ught : on May 13th I again turned 

 the dish 180^, and found on the 26th of May that the shoots 

 again were be^nt towards the hght. (Figs. 1 and 2.) 



It is already known that in uniform light, the leaves of 

 Schistostega generally turn in all directions, l)ut that when the 

 light is unilateral, their divergence is -y . After putting a cultur- 

 ing dish in a dark room for seven months, beginning with Novem- 

 ber 14th, I found that only the protonemata were alive. Not a 

 single leafy shoot had been produced ; but the green colour of the 

 chromatophores had not wholly disappeared. It is also interesting 

 to observe that the shoot is shorter and the leaf larger in a feeble 

 than in a comparatively intense light. Placed in a position where 

 the intensity of light is above 0.1, the colour of the moss gradually 

 disappears from all its parts, changing into a silvery white after 

 the lapse of from seven to ten days. This is owing to the dis- 

 appearance of the colour of the chromatopliores and of the de- 

 struction of the lens-shaped cells. Under such circumstances the 

 moss soon loses its vitality. In comparing the formation of starch 

 in the lens-shaped cells of the protonema with that in the filament- 

 ous cells, we find that it is greater in the former than in the 

 latter. From this fact and also from that, that a fairly large 

 percentage of sugar exists in the lens-shaped cell, it is inferred, 

 that by virtue of these lens-shaped cells this moss can effect 

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

 a stronger light. 



3. Movement of the Chromatophore. — -By the studies of 

 Noll and Senn, it has l)eon fully established, that the light which 

 is reflected from the lens-shaped colls is caused by its peculiar 

 optical structure. The reflected emerald green-light which re- 

 appears after tlie culturing dish has been turned 180 degrees. 



