21 
THE FIBRO-VASCULAR SYSTEM. 
The fibro-vaseular system of the embryos of the Graminew may be 
considered under three main divisions, according to the manner and 
place of insertion of the plumule-sheath on the axis and its connection 
with the scutellum. 
1. Thé plumule-sheath is inserted on the axis directly above the 
insertion of the scutellum: Stipa (fig. 36, Pl. V), Phlewm (fig. 41, Pl. V), 
Ammophila (Fig. 42, Pl. Vy, and perhaps all of the Agrostidec. 
An example of this modification oceurs in Stipa viridula (figs. 32 and 
33, PL IV). A vaseular bundle passes through the entire length of 
the scutellum. At the insertion of this bundle on the axis two branches 
are sent off from it which traverse the plumule-sheath (fig. 33, Pl. IV), 
while the main branch continues into the axis and then descends to the 
radicle, A little above this insertion numerous small bundles form and 
run up into the young leaves and vegetation point. Asthese different 
bundles are not all in the same plane, it is not possible to obtain a sin- 
gle seetion showing them. In any transverse section of the plumule, 
however, the bundles of the plumule-sheath may be seen quite dis- 
tinetly. 
In Eriocoma cuspidata (fig. 34, Pl. IV) the bundles ascend from the 
axis into the plumule-sheath, while in a cross section of Stipa richard- 
sonii (fig. 37 B, Pl. V), taken below the insertion of the scutellum on the 
axis, the vascular bundle may be seen entering the radicle. Again, in 
Triticum (fig. 69, Pl. VII) a bundle may be seen entering the first true 
leaf. Hordeum (fig. 65, Pl. VII) shows the bundles passing up into the 
second true leaf and the vegetation point, while several may be seen 
branching off from the axis into the secondary radicles. All the genera 
of the tribes Agrostidee and Hordee, so far as examined, have this 
arrangement of their vascular systems. : 1 
2. The plumule-sheath is inserted on the axis at some distance from 
that of the scutellum, with whieh it is connected by a vascular bundle 
traversing the axis: Zizania (fig. 22, Pl. III) and Homalocenchrus (fig. 
28, Pl. IV). The embryo of Zizania aquatica (figs. 22, 23 A - B, 24 
A-T, Pl. III) has a remarkably long axis, which separates the insertion 
of the plumule-sheath and the scutellum to a very considerable degres 
It will be noticed in the longitudinal section (fig. 22, Pl. LIT) that two 
vascular bundles traverse the axis, one terminating in the main radicle, 
while the other curves sharply round and traverses the long linear 
seutellum. The exceedingly large epiblast is devoid of any vascular 
Kaum. hs thetrüustorio sections (e 14 A-T, PL IL) itis found that 
in A, a section taken through the apex of the plumule-sheath, the two. 
bundles have joined into one. In B they are beginning to separate, 
while in © and D they are entirely free. Figure E shows à m aca 
through the tip of the first leaf of the plumule, the ee + L 
its two widely separated lateral bundles surrounding it. 5 e 
illustrate sections taken through the plumule at different heights, show- 
ing the arrangement of the leaves with their bundles. The bundle in 
