396 BOTANICAL GAZETTE [DECEMBER 
To this last observation I have two others to add, namely, 
the occurrence of an internal phloem in which the sieve tubes 
form a more or less continuous ring (figs. 2z, and 22), and in 
rare cases the union of external and internal phloem through a _ 
leaf gap. Inacertain rich, moist situation about a dozen well 
nourished plants of O. cinnamomea grew, of which, on examina- 
tion, five showed the phenomenon of a continuous layer of inter- 
nal phloem. Search in an adjoining locality resulted in finding 
specimens which showed the same feature. To extend the range 
of observations, I visited a peat bog some twenty miles distant 
from Toronto, where I knew the cinnamon fern grew, and 
secured specimens characterized by the same peculiarity. ig. 
27 shows a transverse section of a stem found in this last locality. 
The sieve tubes of this internal phloem are as typical as those of 
the external, and except for their position not be distinguished 
from them. They do not always form a continuous ring as do 
the sieve tubes of the external phloem, but are often in more or 
less detached groups, embedded in small celled parenchyma. 
The layer of sieve tubes is from one to three cells thick. It 
should be added that internal phloem occurs only near where 
the forking of the stem takes place. 
O. cinnamomea shows likewise two other features which are 
constant throughout every part of the stem, and at once distin- 
guish it from other species: (1) an internal endodermis, and (2) 
several layers of parenchyma between this and the xylem. 
INTERNAL ENDODERMIS.—The internal endodermis possesses 
the characteristic radial dot, though sometimes not as clearly 
distinguishable as in the external endodermis (17. ¢., fig. 2} Its 
cells are usually larger than those of the latter, but are filled 
with similar contents, most frequently tannin (fig. 75). It is 
further to be noted that it bends outwards opposite the leaf 
gaps (figs ro, etc.), and not infrequently connects through them 
with the external endodermis. I have examined scores of stems 
of the cinnamon fern, and in every specimen there was an internal 
endodermis. On the contrary, it seems to be invariably absent 
from the other species studied. As the central cylinder of the 
