407 
Arum maculatum from the Seed. 
( 
example, as that drawn in Fig. 4. A transverse section 
passing through the cotyledon and the stem-bud just above 
the insertion of the latter on the axis, shows the cotyledon as 
a ring of tissue studded with five vascular bundles. Within 
it are three concentric rings which represent the three leaves 
already mentioned. A fourth rudimentary leaf is indeed 
present, but as it will not come to maturity in the following 
year, we are not now concerned with its structure. 
Each of the two outer leaves displays three bundles, the 
third shows a single procambial strand representing its midrib. 
We can trace these seven bundles in a section taken rather 
lower down, beneath the insertion of the stem-bud but above 
that of the cotyledon. The position of the bundles in such 
a section is diagrammatically shown in Fig. 11. The cotyle- 
donary bundles are numbered 1-5, and of these that marked 
3 is the midrib. The circles A, B, C represent the traces 
of the first leaf ; a, (3, y, those of the second. The midrib of 
the third leaf is called /. In the node next below this inter- 
node, the course of the bundles is indicated by the arrows 
in the diagram. The inmost circle of traces, a, [3, y, bend 
inwards, and with the midrib /, which forks to the right and 
left, they form an incomplete vascular girdle. The phloem 
of the four bundles indeed forms a continuous ring, within 
which are the groups of xylem. These, though extended 
tangentially, do not yet unite to form a ring ; the xylem of 
the midrib always remains quite distinct from that of the 
other bundles. The xylem groups of the latter stretch out 
in a broken crescent fronting the midrib — an arrangement 
very characteristic of the young node. It is well shown in 
Fig. 15 which represents the first node of the young stem. 
The node just described is the third of the young stem, and 
from it arises the first whorl of roots. When the roots are 
fully formed, as in the seedling drawn in Fig. 6, a section 
through their insertion shows the formation called by M. Van 
Tieghem the ‘ reseau radicifere V The xylem as well as the 
1 Van Tieghem, Traite de Botanique, 2nded., Vol. i, p. 787. 
E e 2 
