572 Hatfield,— Anatomy of the Seedling and 
cylinder, i. e. removed by 1 8o° from the position of the leaf midrib (com- 
pare Text-fig. 3, c). 
We see, therefore, that there are no ‘ direct ’ and no * girdling ’ traces 
for the first foliage + leaf, but that all pursue a more or less oblique 
course, and that the most oblique strand of this leaf encircles the axis 
for qo°, or rather less. The second leaf, on the other hand, has both 
‘ direct * and ‘ girdling ’ traces — i. e. traces which encircle the axis for i8o°. 
In this leaf, then, the typical Cycadean vascular supply is established. 
We have thus established, at the cotyledonary node, the vascular 
arrangement figured in Text-fig. 3, C. The cotyledonary traces are 
grouped diagonally ; there are three traces in each cotyledon, and they 
are arranged in groups of two traces and of one respectively, opposite 
to the primary medullary rays. They now pass rapidly inwards (Text- 
fig. 4) through these medullary rays ; the xylem and phloem masses of 
cotyledon and leaf-traces fuse, and so an irregular central vascular 
cylinder is formed, which soon becomes the typical protostele of the 
upper region of the hypocotyl (Text-fig. 1). 
II. The Young Plant. 
A . External appearance. These plants (Plate XXII, Fig. I), which have 
produced some twenty leaves, have a short, tuberous stem, about 5 cm. long, 
clothed with persistent leaf-bases, a swollen turnip-like hypocotyledonary 
region, and a long, little-branched tap-root. A definite constriction occurs at 
the cotyledonary node. The expanded foliage leaves, about six in number, 
are of a varying age — the fully-formed leaf being some 80 cm. in length, and 
bearing between 60 and 70 pinnae. Several — generally three — rudimentary 
leaves are to be distinguished at the stem apex. Below the apical region 
are fleshy and persistent leaf-bases ; these are reduced in length by the 
formation of successive periderm layers, until, at the base of the stem, such 
remains are only 1 cm. in length (Text-fig. 8). 
B. Internal structure : (1) The leaf. In very young leaves a layer 
of stone cells, with lignified walls, surrounds the primordium of each future 
vascular strand. The fleshy base of a mature leaf is packed with starch ; 
it is traversed by about ten endarch vascular bundles, which are arranged 
in an open arc. There is no extra-vascular strengthening tissue. Above 
the leaf-base the petiole is no longer fleshy, and contains little starch. 
Stone cells are found in groups in the sub- epidermal tissue. As the region 
of insertion of the pinnae is approached, these form an almost continuous 
layer — several cells thick— beneath the cuticular epidermis ; in this region 
they are also found surrounding the vascular bundles. Numerous bundles, 
derived from those of the base by repeated dichotomy, and arranged on 
the il plan, traverse the petiole. These bundles are mesarch in the middle 
region of the petiole, becoming exarch towards its distal end. Two traces, 
