VII. 



ON CHLOROCYSTIS SARCOPHYCLA NEW 



ENDOPHYTIC ALGA. 



WHEN Mr. Bracebridge Wilson was collecting Sarcopliycus, he observed 

 the occurrence of raised circular patches, forming gall-like structures 

 on certain of the fronds. He collected and sent to the British Museum, 

 for the purpose of investigation, material on which such patches occurred, 

 saying that he found them to be caused by what he took to be an 

 unicellular Protococcaceous Alga. An examination of this material, 

 which was put into my hands, has proved that this is indeed the case, 

 and I will proceed to a description of these peculiar patches and the 

 endophyte producing them. 



The patches (plate XII., figs. 4, 5, 6) vary in size from a quarter of 

 an inch to one inch in diameter, and are generally circular, but sometimes 

 rather oval in form. They are accompanied by a bulging of the frond 

 causing malformations, of which, while one surface is raised above, the 

 other is somewhat depressed below the surrounding portion of the 

 frond. The surface generally presents either a smooth or a corrugated, 

 rough, and decomposed appearance, sometimes only one, and sometimes 

 both surfaces being thus affected. 



These malformations are caused by the growth of an unicellular 

 endophytic Alga in greater or less abundance between the filaments 

 of the cortical portion of the thallus. 



The endophytic cells (plate XIL, fig. 10) are thin-walled, chloro- 

 phyllaceous, various in size, and irregular in shape. They appear to 

 vary in shape according to the pressure exerted upon them by the 

 surrounding portions of the thallus. The cell when young contains 

 homogeneous protoplasm (plate XIL, fig. loa), which at first, completely 

 filling the cell-cavity, often shrinks away later from the cell-wall. 

 Later, by the process of free-cell-formation, the protoplasmic contents 

 become differentiated into a very large number of small spores, which 



