372 G. T. HARRIS OX 



luminous appearance" (fig. 3 in text). Haberlandt states tHat "the 

 chlorophyll apparatus in each funnel-shaped cell is so brilliantly 

 illuminated that it acts against a dark background as a self- 

 luminous body, any rays that are not absorbed by the chloroplasts 

 being reflected and retraversing the whole optical system contrary 

 to their path of entry" (24). When examining the "rosette" 

 chloroplast with a high power I have noticed its surface to possess 

 a decided burnished appearance. The researches of Guilliermond 

 (25) would suggest that this is due to the pigment of the chloro- 

 plasts having assumed a crystalline state, and it will be seen that 

 a highly crystalline state of the concave surface of the chloroplast 

 would practically convert it into a parabolic reflector and explain 

 in a large measure the green effulgence noticeable when looking 

 at a bed of this moss. One remarkable feature of the light-cell 

 producing portion of the protoneraa is the great variety of shape 

 the chloroplasts assume in the effort of dovetailing together to 

 form an unbroken surface of chlorophyll for the light to act upon. 

 Cells number 1 and number 2 in fig. 3, Plate 24, well represent this 

 dovetailing arrangement, which appears not to exist to the same 

 extent in those parts of the protonema not directly connected 

 with the production of light-cells. 



My thanks are due to several who have generously given me 

 help in the preparation of this paper. Mr. W. P. Hiern, M.A., 

 F.R.S., very kindly transcribed and sent me much informa- 

 tion relative to the discovery of the moss in Devonshire and its 

 early history. Mr. H. N. Dixon, M.A., F.L.S., was good enough 

 to look up and send me references to the literature dealing more 

 especially with the morphology of the plant ; while my friend, 

 Mr. F. R. Rowley, F.R.M.S., of Exeter, generously devoted part of 

 his holiday on Dartmoor to investigating the orientation of such 

 beds of Schistostega as he came across. I have again to thank 

 the Quekett Microscopical Club for extending to me the hospitality 

 of its Journal. 



Literature Cited and Consulted. 



1. Dickson, H. S. Fasciculus Plantarum Cryftogamicarum 



Britannae, 1785. 



2. Hedwig. Descrifiio et adwnhratio Muscorum frondosorutn, 



fol. 1787-1797. 



