The Morphology of Ruppia Maritima. io 
The course taken by the cortical bundles, although simple, is not 
quite as evident. The cortical bundles are entirely independent of 
the central bundle, never connecting with it, so far as I have been 
able to ascertain. Their position can be best shown by the use of 
figures selected from a series of cross sections. A cross section in 
the region of a node, just below the point where the leaf is given 
off, is represented in Pl. V, fig. 19. Here the cortical bundles are 
situated in the outer cortex, not quite diametrically opposite each 
other. This figure also shows the axial bundle somewhat dilated 
radially. Pl. V, fig. 20 shows the edges of the leaf sheaths appearing 
at the cleft at the upper side of the figure. The cortical bundles 
occupy about the same position as before, but the axial bundle is 
commencing to give off its two branches—to the leaf and axillary 
branch. In Pl. V, fig. 24 the leaf sheaths are still more separated 
from the stem; the two large leaf and branch bundles are now dis- 
tinct from the axial stem bundle; the cortical bundles have moved 
outward slightly, and a new cortical bundle appears nearer the 
central bundle. Since the section is cut slightly obliquely, and the 
right side represents a portion higher up in the stem, only one of 
the pair of new cortical bundles thus appears. PI. V, fig. 22 shows 
both, however, and also represents the former pair of cortical bundles 
as moving gradually into the still further separated leaf. Pl. V, 
fig. 23 shows the leaf with its lateral (cortical) bundles, separate 
from the stem, and fig. 24 does the same for the branch which 
it subtends. 
It is clear, therefore, that the cortical bundles of the stem furnish 
the lateral nerves of the leaf. It will be seen also that not only 
do the cortical bundles have no connection with the axial bundle, 
but also that a new pair arises at each node to pass into the leaf 
at the node next higher up. After a careful examination, I find 
absolutely no connection between these successive pairs of cortical 
bundles. 
Although the figures and description of De Bary (1884, p. 274) 
for Potamogeton crispus seemed to present an arrangement similar 
to the above, the work of Chrysler (1907), which appeared while 
this paper was being prepared for publication, corrects De Bary’s 
account but confirms my investigation of Ruppia maritima. Chrysler’s 
conclusion (l. c. p. 171) is undoubtedly correct that “ this condition 
has in all probability been derived by reduction from that in which 
the cortical bundles joined the central cylinder at the next node 
below the insertion of the leaf to which they belong.” 
The cortical bundles of Zostera marina (De Bary, 1884, p. 275; 
