SCHISTOSTEGA OSMUNBACEA MOHR. 36^ 



protonema, is spread out in an irregular superficial series of cell& 

 of greater or less extent. 



In examining the protonema of Scliistostega one cannot fail to 

 be struck by the nodular condition (Plate 23, fig. 10) the cells 

 assume, even when they do not develop into the advanced stages 

 shown by the flask-shaped and obconical light-cells. It would 

 appear that any cell is capable of producing a distension that may 

 ultimately become either a flask-cell or a light-cell. The flask- 

 cells were first noticed by Correns (21), who described them as a. 

 form of gemma. Later Grout (22) called attention to them as. 

 existing in gatherings of Schistostega made in America. I have 

 frequently met with them in my own gatherings, and at first,, 

 influenced by the views of Correns and Grout, I regarded them 

 as a form of gemma. This, however, they are not ; being merely 

 the separation cell remaining after the liberation of the true 

 gemma. Fig. 11, Plate 23, shows one of these flask-cells remaining, 

 attached to a portion of the protonema filament, but occasionally 

 the entire filament seems to be given up to the production of the. 

 gemmae, as may be seen from a consideration of fig. 1, Plate 24^ 

 in which numerous separation cells are shown from which the 

 gemmae have fallen ; at -4 a gemma is forming by enlargement of 

 the distal cell, and B shows the initial stage in the production of 

 a flask-cell. It is interesting to note that the globose base of the 

 flask-cells which bear the gemmae often produce the characteristic 

 bowl-shaped chloroplast, as will be seen on reference to Plate 23^. 

 fig. 11, A, and again in Plate 24, fig. 1. c. There appears to be 

 no stability in the form of any of the variously shaped cells to be 

 found in the protonema. The narrow elongated cells may bulge 

 at some point and a light- cell be produced, which may elongate 

 and form a flask- cell, to give rise eventually to a gemma. One 

 of the marked features of all the cells connected with the proto- 

 nema is the large size and heliotropic arrangement of the chloro- 

 plasts, even when single and not bowl-shaped as in the light-cellsw 

 Braithwaite incorrectly describes the protonema as " composed 

 of globose cells void of chlorophyll," and gives a figure that very 

 poorly represents the actual structure. He also figures the leaf- 

 cells as filled with minute grains of chlorophyll, whereas the 

 chloroplasts are quite noticeably large and comparatively few in 

 number, being oval and round and about lOyw. in diameter. The 

 cell itself is about 1/50 mm. in thickness, and the chloroplasts are 

 JouRN. Q. M. C, Series II.— No. 82. 28 



