AND THEIR BEARING ON STELAR THEORIES FOR THE FERNS. 
729 
condition as it merges into the undifferentiated mass of 
the growing apex. From these facts it may he concluded . 
that by early initiation of inner phloem within a purely 
intraxylic pith a Lindsaya structure arises. By change 
of procambial destination the inner phloem may vary in 
amount and position, and the final structure so far evolved 
for the specimen considered is a medullated protostele with 
inner phloem and xylic gaps, but devoid of endodermal 
pockets. 
In text-fig. 7 the general arrangement of stelar tissues 
in another specimen is shown. In its essential features it 
repeats the stelar changes from solid protostely to medullated 
protostely with tubular inner phloem, and xylic gaps recorded II 
from the first plant. The full resemblance to a Lindsaya 
type, as illustrated by Lindsaya adiantifolia, lies in the fact 
that the outer and inner phloem may be connected through 
xylic gaps (I and II). Towards the apex of the stele definite 
endodermal pockets of variable depth are associated with the 
leaf-traces. Text-fig. 8 shows the stelar state in part of an 
adult plant. At the base the inner phloem is tubular, and 
a leaf-trace is departing in the protostelic manner (a). 
Associated with leaf-traces c, d, e, and f are endodermal 
pockets of variable depth. The pith is bulky, and the 
inner phloem is a wide tube more or less coaxial with the 
xylem-cylinder. Fig. 39 shows the stelar structure at I, 
and illustrates the stelar expansion which has been effected. 
Passing upwards, endodermal cells appear in the pith (En/, 
fig. 40). These form the base of a pocket (P, fig. 41 ; p, text- 
fig. 8), which opens into the first foliar gap (g ; andG, fig. 42), 
and extends onwards into a succession of them (g 1 , g 2 , and 
g 3 ). Thus, as in Gleichenia pectinata , a continuous inner 
endodermis is established, and solenostely is attained. Fig. 43 
shows the full solenostelic structure at II. The pith (M) is 
here a continuous column of more or less sclerotic tissue like 
the cortex without, to which it is directly linked through the 
succession of foliar gaps. t 
No structural evidence has been found of sliding growth 
or cortical intrusion to which the establishment of soleno- < 
stely could be referred, but the study of the growing point 
has led to the conclusion that here, as in other organisms 
already considered, the successive changes of stelar structure 
Text-fig. 8. 
