Tilden: pilinia and stigeoclonium. 625 



3 . Palmella Stage. As has been previously stated, cells 

 of the Palmella type form an ever present element in the Pil- 

 inia material. When the first examination was being made the 

 contents of these cells were noticed to be in process of division 

 and afterwards to pass out as motile spores. No notes nor 

 drawings were taken of this at the time, but before the end of 

 the week, I began keeping notes regarding their behavior as 

 well as that of Pilinia in case they should be found to be a 

 stage of that plant. 



Cells of this nature were seen in two conditions: (1) Soli- 

 tary, either lying entirely alone or in heaps or piles. (2) Con- 

 nected, either in small groups or in extensive plates. 



(1) The isolated cells have the following characteristics: 

 They average from 10-15 mic. in diameter, are in general per- 

 fectly spherical in shape, densely filled with chlorophyllous 

 contents containing coarse granules and occasionally others 

 of different sizes. In many cases a portion of the contents is 

 colorless. The enveloping wall is in most cases distinct. When 

 it shows at all, it varies in width from a delicate though firm, 

 smooth membrane to a wide gelatinous band. Near the center 

 of the cell there generally appears a lighter spot. 



Some of these cells were frequently seen undergoing divis- 

 division into 2-4-8 parts. The contents were finally granular. 

 The size of the newly formed bodies varied from 3-7| mic. (PL 

 XXXIV, fig. 3). The pyrenoid lying in the center of the original 

 cell indicates the formation of the first wall by separating 

 into two. These lie opposite each other with the new wall be- 

 tween (PL XXXIV, fig. 3a). Another division of each pyrenoid 

 again occurs as four internal spore portions become separated 

 off, and so on until a certain number of spores are formed. A 

 spherical cell 14 mic. in diameter is shown dividing into four por- 

 tions (PL XXXIV, fig. 3b). It occured in a group with others 

 not yet undergoing division and still others already emptied of 

 their contents. With them were seen spores 5 mic. in diameter. 

 A spherical cell 12. 5 mic. in diameter contained four spores 5 mic. 

 in diameter, showing eye- spots. Another group was present 

 in which were the large solitary green cells piled loosely 

 together. With them were several colorless cysts of the same 

 size, 13 mic. in diameter. One of these still retained two spores 

 5 and 7 mic. in diameter. 



Plants of this kind taken from pebble "4" were found to be 

 entirely healthy in appearance. The contents were uniformly 

 green in color, coarsely granular, and the outside membrane 



