400 Wiscojhsiii Academy of Sciences, Arts, and Letters. 



but in old, well developed cells is evenly distributed. Tbis 

 layer also contains starcli vesicles (pyrenoids) tbat project 

 into tbe central vacuole on tbe inside. 



Wliile tbe above description lacks many important details 

 and is in error as to tbe differentiation of tbe protoplast into 

 layers, it is notable tbat later observers using tbe same metbods 

 as Braun, bave made very little advance beyond tbe results be 

 obtained as to tbe structure of tbe cell contents. 



Tbe cell wall is also, according to Braun, comjwsed of tbree 

 layers as follows: 1. An outer, tbin cuticle. 2. A middle 

 tbick layer, tbat swells strongly in sulpburic acid and stains 

 blue witb iodine. 3. An inner laver tbat swells so as to be- 

 come tbe tbickest of tbe tbree wben treated witb sulpburic acid 

 and to present wavelike folds on tbe inner surfaces. 



In tbe account of tbe spore formation Braun described only 

 some stages tbat belong to tbe later pbases of tbe cleavage of 

 tbe wliole protoplasmic mass, lie determined, bowever, tbat 

 preliminary to tbo beginning of tbe process tbe pyrenoids 

 (starcb vesicles) disappear, Tbe first stage of cleavage con- 

 sists, as be described it, in tbe appearance in tbe protoplasm, of 

 numerous liglit spots equidistant from eacb otber between 

 wbicli tbe granides of cbloropbyl arrange tbemselves in rows. 

 Tbis stage is followed by one in wliicb tbe granules retreat 

 toward tbe clear spots, leaving transparent lines tbat mark off 

 bexagonal areas on tbe surface. Eacb mass tbus formed 

 finally becomes a spore. Tbe transparent lines are supposed to 

 be of some substance tbat separates tbe bexagonal masses, and 

 is dissolved during tbe subsequent process of tbe complete sep- 

 aration of tbe spores, wben tbe lines disappear except for tri- 

 angular spaces between tbe rounded masses. 



After a period of rapid movement inside tbe motber cell wall 

 tbe swarm spores come to rest and form a new net. Tbe pyre- 

 noids begin to appear immediately after tbe swarm spores bave 

 come to rest. Braun beld tbat tbeir origin was entirely de 

 novo and tbat tbey were never multiplied by fission. 



In some cases swarm spores were observed wbicb bad two 

 or more pairs of cilia. Tbis was accounted for by tbe non ap- 

 pearance of tbe ligbt cleavage lines in an earlier stage. It is to 



