188 BOTANICAL GAZETTE . [September 



says that the spores enlarge strikingly at first, and by one-sided 

 growth a filament is formed which elongates by apical growth , 

 forming a cylindrical body. This body branches and in the tip 

 cell of the main axis and its branches the typical apical cell of the 

 mature thallus arises. 



In Aneura pinguis the spores at shedding contain chloroplasts 

 as mentioned above (fig. 51). The spore does increase rapidly in 

 size from 60 and 70 p to 90 and 100 fi in a few days. The plastids 

 are grouped somewhat at one side, where the cell begins to elongate 

 into a slight projection. A wall divides the spore into two unequal 

 cells (fig. 56) (this may happen within 1 or 2 weeks) ; the smaller one 

 grows until it equals the sister cell. The exospore has not been 

 split, but has elongated and surrounds the two cells (figs. 57, 58). 

 The younger cell is now divided unequally by a vertical wall bent 

 slightly toward the long axis of the cell (figs. 59, 60). It soon grows 

 as large as the cell from which it was cut off, and the division could 

 easily be mistaken for an equal one. This division may also be 

 horizontal, resulting in a dorsal and a ventral cell. The apical cell 

 may originate in either one of these two cells, probably the better 

 lighted one (Peirce 22, Lampa 16 and 17, Goebel 10-12, 

 Bolleter 2, Schostakowitsch 24). This second or third wall 

 can then be considered the one which marks out the apical cell. 



Only one sporeling was found where the exospore had split and 

 a filament of five cells had grown (fig. 71). The next division comes 

 when the last cell cut off equals that from which it was cut, and the 

 new wall again is a vertical one inclined toward the axis of elongation 

 (fig. 61). This mode of development continues up to the four- and 

 five-celled stage. The only difference between this apical cell and 

 that of the mature thallus is the longer time interval between the 

 segmentation and the division of the segments. In this four- and 

 five-celled stage the echinate projections of the exospore are still 

 present, at a greater distance apart and finally disappearing. The 

 mass of cells looks slightly as has been pictured for Lejeunia serpyl- 

 lifolia (Campbell 3). 



This then reduces Aneura pinguis to the condition described by 

 Goebel (12) for Metzgeria furcata, where the filamentous stage or 

 Vorkeim consists of one or two cells. The branched filaments are 



