726 
DR JOHN M'LEAN THOMPSON ON NEW STELAR FACTS, 
tract. But that both these tracts of pith are referable in origin to the pro- 
cambial mass of the growing point seems the only reasonable interpretation of the 
ontogenetic facts. They are thus viewed as one continuous medullary field across 
which a barrier of inner endodermis has been constructed by static changes of 
procambial destination during the ontogeny. Here, as in the other organisms 
considered, the inner endodermis provides an increase of endodermal area by 
which the physiological control of the conductive cylinder may be enhanced. 
Of these organisms Gleichenia pectinata is considered the most advanced in stelar 
structure, the collective attainments of the others in regard to stelar amplification 
being repeated in its ontogeny. To these are added solenostely and foliar gaps. 
On the view of static ontogenetic change of stelar structure here adopted, the foliar 
gaps of Gleichenia pectinata are of similar origin to endodermal pockets ; but while 
the latter are closed at their base and do not permit of histological continuity 
of pith and cortex, the former are open channels through which pith and cortex, 
originally distinct, unite to form one continuous tissue. 
The general position adopted on the facts described is that stelar tissues of any 
category may be formed where and when required within the confines of the stele. 
Protostely with medulla, endodermal pockets, and sporadic inner endodermal spindles 
is the high-water mark attained by intrastelar changes for the species of Schizsea 
dealt with : Gleichenia fidbellata has acquired endodermal pockets alone, and Platy- 
zoma has not advanced to the solenostely shown by Gleichenia pectinata , being 
still devoid of stelar gaps and inner phloem. 
Gleichenia pectinata is a solenostelic member of the “ Superficiales,” thus 
resembling such organisms as Metaxya, Lophosoria, Matonia, and Dipteris, which 
possess solenosteles and superficial sori. The ontogenetic facts for the latter genera 
are unknown, but grounds for further comparison may be found in the stelar 
ontogeny of examples of the “ Marginales,” which will now be considered. 
Lindsaya adiantifolia. 
Pacts of adult structure for a number of the Lindsayas have been provided by 
Tansley and Lulham (59), Gwynne-Vaughan, and others. The internode in the 
Lindsaya type shows a dorsiventral stele with parenchymatous xylem-core in which 
a continuous internal strand of phloem and parenchyma runs close to its dorsal 
surface, and is linked to the outer phloem of both leaf-trace and stele at a xylic gap. 
These gaps are in the axils of leaf-traces, and through them endodermal pockets are 
decurrent into the internal phloem. In the adult stele of a Lindsaya the stelar 
endodermis is thus unbroken. The general arrangement of stelar tissues as seen 
in longitudinal section is represented in text-fig. 4 ; xylem is solid black, parenchyma 
is white, phloem cross-hatched, and endodermis an unbroken line. The ontogeny 
of Lindsaya adiantifolia opens with a solid protostele. Its xylem-core becomes 
parenchymatous as it expands (fig. 31). Phloem forms an narrow unbroken band 
