26 NATURAL HISTORY SOCIETY OF LUBLIN. 



But the plant I identify as M. clilamydosporum (De Bary), or which 

 perhaps I believe I might possibly be more correct in assuming as a 

 variety thereof, I had at first thought to be a distinct species, and so, 

 indeed, it may possibly still prove to be ; and I had, when this paper 

 was read, drawn up a description of it as such ; but if I err in modifying 

 my former opinion, it is at least an error on the right side. I shall, 

 however, endeavour to put forward a general description of the plant 

 which occurs here, reserving an allusion to the points in which it differs 

 from De Bary's, until after a brief reference to the generally received 

 views as to the affinities of the genus. 



Mesotcenium clilamydosporum (De Bary). 

 Yar. /3. 



General Description. — Mass light green, gelatinous, rather firm ; cells 

 oblong, cylindrical, ends broadly rounded ; chlorophyll-plate in edge 

 view, usually axile, narrow, fusiform, pointed at the ends, which do not 

 reach the extremities of the cells, after division blunt at the ends towards 

 the septum dividing the mother-cell ; nucleus, when to be seen, forming 

 a small rounded body, lying upon one of the front surfaces of the plate ; 

 granular contents very dense and abundant, often preventing the view 

 of the chlorophyll-plate, which is therefore very rarely discernible in 

 front view. Conjugation effected by the extension and protrusion of the 

 entire contents, which touch and incorporate at any point, the parent 

 cells uniting in many varieties of position, the original cell-membrane 

 of each being thrown off, in its almost original form, each half often bent 

 at an angle, as if due to a separation at a suture. Zygospore, at first 

 shapeless or irregular, assuming finally an ovate or elliptic outline, and 

 becoming surrounded by a comparatively thin, sharply-defined mucous 

 envelope, the cell-contents very dense and coarsely granular, the latter 

 ultimately becoming considerably retracted from the outer wall and sur- 

 rounded by an inner, finally yellowish or brownish coat, forming the 

 actual spore, which presents to view a four- five- or six-sided, or a 

 somewhat circular outline, sometimes somewhat flattened at certain sides, 

 slightly enlarged or thickened at the angles, and often presenting on the 

 general surface a slightly undulate or somewhat granular appearance, 

 due to the presence of little superficial prominences. When showing 

 four sides, I presume the inner spore may be of a cubical or prismatic 

 figure, and when 5- or 6- sided, irregularly polygonal, but it appears some- 

 times of an irregularly rounded, very indefinite form. I have not seen, 

 however, a triangular form. 



Measurements. — Length of cell, T ^ ^ to 7 -f ^ ; breadth of cell, 2^50 > 

 length of zygospore, -g^ to g-^ ; breadth, yj^o to gjj of an inch. 



Plate I., Fig. 1, cell in which the chlorophyll-plate cannot be seen; 

 either the remaining contents are too dense, or the edge view of the plate 

 is not towards the observer. Fig. 2 shows edge view of chlorophyll- 

 plate, with nucleus (?). Fig. 3-4, accidental forms and positions of the 

 chlorophyll-plate. Fig. 5, cell about to divide ; the chlorophyll-plate 



