246 Annie C. May brook. 
Form V, there were no air chambers, ventral scales or tuberculated 
rhizoids. A few smooth-walled rhizoids were produced on either 
side of the midrib, the latter being somewhat less pronounced than 
in Forms I, II and III. The structure of the individual thallus was 
uniform throughout, shewing complete absence of assimilating tissue 
and mucilage sacs (Fig. 1, 8). The epidermis contained numerous 
chloroplasts which were ranged along the upper walls of the cells 
(Fig. 1, 9). The rest of the thallus consisted of large colourless 
storage cells containing starch grains. The walls of the storage 
cells were not thickened by anastomosing bands of cellulose as in 
Forms I, II and III. 
There has been no previous record of the occurrence in nature 
of forms of Fegatella conica without air chambers, although, in the 
light of recent observations on Dumortiera, 1 one is led to suspect 
that, given the necessary conditions, such a form would arise. The 
only conclusive evidence that the thalli of Forms IV and V belong 
to Fegatella conica would be one of culture, but it is very improbable 
that they should belong to any other member of the Marchantiales 
—firstly, because Fegatella conica was the only liverwort growing 
anywhere around, and secondly, because of the existence of the 
transitional form described below. Maheu 2 describes the general 
appearance of Fegatella plants growing in the most feebly illuminated 
deeper portions of ditches, stream-sides, and holes; in extreme cases 
there was practically no rosette formation, the individual plants 
being greatly elongated (as long as 25 to 30 cm.), very slightly 
branched (usually only once), very narrow (less than 5 mm. broad), 
extremely thin and tinged only slightly green so as to be quite 
transparent, while the dome like roofs of the air-chambers were 
absent and the upper surface of the thallus thus quite flat. 
It has already been shewn how a reduction in the fractional 
light intensity has been accompanied by a reduction in the size of 
the thallus, and in the number and size of the air chambers (see 
Table). Now among the thalli of Form IV were found a few pieces 
which possessed air chambers, but which shewed a nearer approxi¬ 
mation to thalli of Forms IV and V than did thalli of Form III. 
Compared with thalli of Form III, the air chambers of this 
transitional form shewed a reduction in number, namely 28 per sq. 
cm. as compared with 32 per sq. cm. in Form III. The average 
1 W. C. Coker. “ Selected Notes. II. Liverworts.” Bot. Gazette, Vol. 
36, 1903, p. 225. 
2 J. Maheu. “Monographic des principales deformations des Muscinees 
cavernicoles.” Compt. rend. Congr. Soc. sav., Paris, 1907, p. 343. 
