44 Chlorocystis Sarcopkyci. 



These, when cut across perpendicularly to the surface, show a very slight 

 amount of swelling in the cortical tissue of one or both surfaces, the whole 

 thickness of the tissue in the diseased portion being slightly greater 

 than that of the surrounding portions of the frond. A section of the 

 raised surface of such a malformation (plate XII., fig. 7) will show the 

 endophytic cells between the somewhat swollen filaments of the cortex, 

 thus diverting these from their perpendicular course. Although cells 

 containing spores may occur, yet the contents are for the most part of 

 homogeneous protoplasm. 



Secondly, there are those of which one surface at least is rough and 

 disintegrated, and when cut across show increased swelling in the cortical 

 tissue, the whole thickness of the tissue being considerably greater than 

 that of the surrounding portion of the frond. A section (plate XII., fig. 8) 

 shows endophytic cells in the greater number of which spore-formation 

 has taken place among the cortical filaments which are in this case 

 swollen and becoming separated from each other. In parts the individual 

 cells have become rounded off from each other, forming a loose tissue 

 which at the surface is completely broken down into a discoloured mass 

 of disorganized cells. It is by this decomposition of the filaments sur- 

 rounding them that the endophytic cells are set free. As the decomposition 

 proceeds, the endophytic cells in deeper portions of the cortex are enabled 

 to escape ; in some cases this escape is facilitated by the exfoliation of 

 large portions of the diseased cortical tissue. 



Thirdlv, there are those which when cut across show that the thickness 



* ' 



of the thallus is considerably less than in the surrounding portions of the 

 frond, owing to the destruction of a portion of the cortical tissue. A 

 section (plate XII., fig. 9) shows the loose tissue described above broken 

 down at the surface into a disorganized mass without any remaining 

 endophytic cells. These, in fact, have all escaped from the tissue. 



It appears, then, that the cells of Chlorocystis Sarcophyci are able, in 

 some manner (and perhaps especially during the process of spore-forma- 

 tion), to exert an influence upon the surrounding tissue, causing at first 

 swelling and loosening of the tissue, and finally complete disintegration of 

 the cells. In this point it differs from the species that have been hitherto 

 described, for these inflict no injury on the plant in which they live. The 

 three stages described above may, however, occur in one and the same 

 malformation, for the disintegration proceeds centrifugally, and in many 

 cases a gradation occurs from a peripheral portion, of which the cortex 

 is almost uninjured, to a central portion, in which it is completely dis- 

 integrated. 



The disintegration of the tissue may proceed still further, for Mr. 



