28 Bower.—Studies in the Phytogeny of the Filicales. VII. 
venation of the leaf is open. The structure of the sorus (shown in surface 
view in Hooker’s Tab. CXXXII) corresponds in essentials of structure, 
though not in position, to that of L. aurita. 
The chief point is the absence of an inner indusium, which has been the 
reason for various authors ranking the plant under Pteris. 
But it is these intermediate states, leading to synonymy, which provide 
the foundation for phyletic sequences. The receptacle is very narrow, and 
the underlying commissure a compact strand. The origin of the sporangia 
is clearly intramarginal, and their number small, so that their sequence 
is not obvious. Paraphyses are few or none. It thus appears that in 
vascular characters, in investiture, in venation, and in soral characters the 
species of Lonchitis occupy an intermediate place between the bi-indusiate 
types and the genus Pteris. 
Pteris (. Histiopteris ) incisa (Thunbg.), J. Sm. 
This widely-spread species is specially interesting in view of its similarity 
in habit to Pteridium aquilinum , having a creeping rhizome and widely 
spreading, but glaucous, leaves. Sir W. Hooker 1 notes the variable venation 
of this Fern. Sometimes it is wholly free, as in P. aquilinum ; sometimes 
it is variably anastomosing, after the manner of Litobrochia. Though there 
is a prevalence of hairs, scales do occur on the rhizome. In both of these 
characters the species indicates an advance on the condition of Paesia or 
Pteridium. The habit and dimensions are variable. Sir W. Hooker 
notes 2 a scandent variety 30 feet long ; but the common type is like 
Pteridmm , with buried creeping rhizome and upright leaves. 
The adult anatomy is already known through the work of Tansley and 
Lulham. 3 Though less complicated, it shows analogies with the involved 
structure seen in Pteridium . In a younger state it is simply solenostelic, 
and being a species of considerable size, it seemed a favourable case for 
studying afresh the ontogeny of a solenostele. This has already been traced 
in P. aquilinum by Leclerc du Sablon 4 and by Jeffrey. 5 But as neither of 
these writers has adequately described and delineated the critical point of 
transition from the Linds ay a- condition to solenostely, the detailed observa¬ 
tion of it in a favourable example seemed desirable. 
Several young plants of Pteris incisa collected at Wentworth Falls, 
Australia, were cut into serial sections, and comparison of them gave the 
following results. At first, as in Pteridium aquilinum , 6 the stele of the axis is 
seen to have a solid xylem-core, with occasional parenchyma cells associated 
with the tracheides. As it enlarges upwards, the parenchyma increases at 
the centre, thus forming a parenchymatous pith. The stele then is composed 
1 Sp. Fil., ii, p. 231. 2 l.c.,p. 231. 
3 New Phyt., iii (1904), p. 1. See also Tansley’s Lectures, p. 77. 
4 Ann. Sci. Nat. (1890), Ser. 7, vol. ii, p. 1. 
6 Traps, Can. Inst., vol. vi (1900), PI. VII, 6 Sablon, 1 . c., Fig. 3. 
