66o 
Campbell . — Structure and Affinities of 
The Primary Root. 
The primary root in Macroglossum , as in the other Marattiaceae, has 
a single initial cell. This appears in longitudinal section nearly triangular 
in outline, but is sometimes more or less truncate below (Text-fig. 4, A). 
The cross-section also is irregularly triangular in outline (Text-fig. 4, B). 
There was not available sufficient material to make a complete study of the 
apical growth of the primary root, and it is probable that an examination 
of a considerable number would show some variation in the form and 
segmentation of the apical cell. The root- 
cap, as in the other Marattiaceae, is derived 
in part from lateral segments of the apical 
cell, and the arrangement of the cells of 
the root-cap is quite irregular. 
In the later roots, as in other Marat- 
tiaceae, the single initial cell is replaced 
by a group of similar initial cells, but no 
detailed study was made of these larger 
roots, which do not apparently differ 
essentially from the other forms that have 
been studied. 
The primary root in all cases observed 
was diarch. The endodermis is not as 
conspicuous as is often the case, and its 
cells were not of uniform size. Outside 
the endodermis was an irregular zone of 
cells infested by a mycorrhiza similar to 
that in the prothallium. This occurrence 
of a mycorrhiza in the primary root has 
been noted in other Marattiaceae. 1 
The second root may show a triarch 
bundle (Text-fig. 5,d), and as the roots be- 
come larger the number of xylems increases. 
The first and second leaves of the young sporophytes are destitute 
of stipules, which first make their appearance in the third leaf (PI. XLVI, 
Fig. 9). These first stipules are small, with somewhat serrate margins. 
The stipules become large in the later leaves, and soon are very con- 
spicuous (PI. XLVI, Fig. 11). These large stipules are joined in front by 
a commissure, and completely enclose the next younger leaf. 
The nature of the vascular system in the stem of the Marattiaceae has 
been examined critically by the writer, 2 and the conclusion was reached 
that no true cauline stele was present in the young sporophyte, whose 
1 See Campbell, loc. cit. 2 See Campbell, loc. cit. 
Text-fig. 4. a, Longitudinal section 
of apex of first root, showing the single 
initial cell (x). x 250. u, Transverse 
section of root-apex, x about 250. 
