310 Bowers — The comparative examination of the 
in Ceratopteris 1 that the succession of three segments from 
the sides and then one from the base is not strictly main- 
tained, but that the number of segments cut off from the 
sides is considerably greater than three to each segmentation 
from the base : differences of detail may also be noted in the 
further subdivision of the segment ; but still, putting aside 
these exceptions, the type for the roots of all the leptospo- 
rangiate Ferns, including also the Schizaeaceae, seems to be 
quite clearly definite, and constant. This uniformity of struc- 
ture makes those deviations from that type, which will now be 
described for the roots of the Osmundaceae, more noteworthy 
than they would otherwise appear. 
An examination of the apex of the root of the Osmundaceae 
has shown that its structure does not conform strictly to this 
simple type of the leptosporangiate Ferns, while there is con- 
siderable variation in detail, even in different roots taken from 
the same individual plant. Among the many roots of Osmunda 
regalis which I have examined, some few show a certain 
similarity in the confocal type : thus in transverse sections a 
single three-sided pyramidal apical cell may occasionally be 
found ; but even when this is the case the structure does not 
show that diagrammatic regularity which is so characteristic 
of the roots of the leptosporangiate Ferns (Fig. 2). Other roots 
of Osmunda show in transverse sections other irregularities, 
such as a single four-sided apical cell, or two such four-sided 
initial cells, etc. ; but of all the aberrant modes of arrangement 
of the cells of the apical meristem found in the roots of Osmunda 
regalis , that which is most interesting from a theoretical point 
of view is that represented in the Figs. 3, 4. In these 
figures it may be seen that the whole tissue is referable in its 
origin to three initial cells, which are marked (x), while the 
three walls separating these cells from one another meet at a 
central point. These three walls are drawn in heavier linesdn 
the figures, and may be traced for some distance from the central 
point : they may be called the principal walls. In each case the 
portion of tissue derived from one of these initial cells is 
1 Parkeriaceae, p. 48. 
