514 Shove.—On the Structure of the 
spicuous in the young than in the mature steles, as is seen by 
comparing Figs. 21 and 25. 
The phloem is of greatest breadth on the side of the stele 
turned away from the axis of the stem, a fact that has been 
already noted by Mettenius and others. This is not very 
obvious in the stele shown in Fig. 21, owing to the crushing 
of the phloem on the outer side, but is seen best by comparing 
Figs. 19 and 28. Fig. 19 shows the edge of the stele in the 
neighbourhood of the protoxylem, and here the phloem-band 
is narrow. Fig. 28 is a drawing of the outer side of the stele, 
and here the phloem, made up of large sieve-tubes and proto¬ 
phloem elements, is of considerable width. The greater 
width of the phloem on the outer side is thus to be attributed 
to the presence here of the protophloem, which, as has been 
mentioned above, is never produced on the inner side of the 
stele. 
The protophloem appears in the mature stele as a dis¬ 
continuous arc of somewhat crushed elements (Fig. 28 pp). 
The centrifugal method of development of the phloem in 
Angiopteris is contrary to that which prevails in other Ferns. 
Thus in the steles of the Gleicheniaceae, Polypodiaceae, and 
Cyatheaceae the protophloem occurs as a similar layer of 
small crushed elements, but the subsequent sieve-tubes are 
developed interior to these. In the genus Matonia 1 , the 
protophloem presents an appearance similar to that in 
Angiopteris , but here again the further development of the 
phloem is centripetal. 
Further evidence in favour of the view that in Angiopteris 
the elements in question really constitute protophloem, lies in 
the fact that no crushed elements occur exterior to the large 
sieve-tubes, but that these border directly on the cells of the 
stem-parenchyma (Figs. 19 and 28). 
In a transverse section of the younger parts of the stem the 
degree of development of the steles is proportional to their 
distance from the centre: thus a stele in the periphery of the 
section may have completely lignified xylem, another nearer 
1 Seward (’99), Fig. 34 . 
