Se) SOAR, ee PSM ee Se tere dE 
Api a Rae a a eae Ra el E E eee 
DR. D. H. SCOTT ON BOTRYCHIOXYLON PARADOXUM. 381 
that of any known genus of Zygopteridex, though the discovery of more complete and 
better-preserved petioles may throw a new light on the question. 
THE APHLEBLE. 
Aphlebize or “ scale-leaves" are borne both on the stem and the petiole. Examples of the 
former case are shown in Pl. 37. fig. 1 and PI. 40. fig. 14, and of the latter in Pl. 37. fig. 4. 
The aphlebiz are different from those of Ankyropteris Grayi (Scott, '12, pl. iv. fig. 7) 
or of A. corrugata (Scott, '08, fig. 117). They are compound, branched structures, and 
their branches have an almost circular transverse section (Pl. 40. fig. 15), so that it is 
easy at first sight to confuse them with roots. They can, however, be distinguished with 
certainty by two characters: the aphlebia has a sclerotic, inner cortex, which does not 
exist in the root (cf. Pl. 40. fig. 16), and the vascular bundle of the aphlebia is very small 
compared with the stele of the root. The aphlebi:e are inserted on the stem by a broad 
base (Pl. 40. fig. 14); the sclerotie cortex extends a little way into the thin-walled cortical 
tissue of the stem or petiole. In the triple aphlebia, shown in PI. 40. fig. 15, two of the 
branches are in obvious connection, and there is little doubt that the third is also part of 
the same organ. As shown at several places, the aphlebiz often braneh at the point 
where they leave the stem, forking into two or more equal limbs. Thus the aphlebia 
shown on a large scale in Pl. 40. fig. 14 is one branch of a double appendage, seen as a 
whole in the general view (Pl. 37. fig. 1), the two main branches running in opposite 
directions, like the thorns of a Robinia. 
The small strands, surrounded by a sheath, which are seen in the cortex of the stem 
(Pl. 38, fig. 6), no doubt supplied the aphlebie ; they can be traced into connection with 
the stele. The fact that these strands occur singly and not in pairs or groups indicates 
that the paired aphlebiz above described are rightly regarded as branches of one, and 
not as distinct organs. 
The details of the vascular strand are not clearly shown; so far as can be seen the 
xylem is a solid strand of tracheides. 
The remarkable appendages which we name 
family Zygopteridez, but those of Botrychioxylon, 
compound spines, are a peculiar and conspicuous feature of our plant. 
aphlebie are characteristic of the 
which might almost be described as 
Tue Roors. 
i i of the 
Adventitious roots are borne on the stem in considerable numbers. In one 
transverse sections (Pl. 37. fig. 2) three horizontal strands are seen passing AD Le 
the cortex, and are clearly those of roots. In the largest the xylem ro m T 
diameter. Free roots are frequently seen outside the stem; a small root ( | wee 
diameter) is shown in Pl, 40. fig. 14). This has a small diarch d xi 2 = 
Cortex consists of a large-celled tissue, while the outer zone is more dense ; 1t 18 
94 
SECOND SERIES.—DOTANY, VOL. VII. 
