Benson.—New Observations on 
1056 
The contrast in character between the metaxylem of the leaf-trace and that of the stem is well 
shown. The stem is partially in a root-bearing phase, x 95. 
Fig. 7. A transverse section of a diarch petiolar bundle. This petiole should be compared 
with the stem in Fig. 8 a. The cusps are not as well preserved as in the petiole shown in 
Fig. 16. Slide 407. 8. x 95. 
Figs. 8 and 9 are low-power micrographs from two successive sections transverse to a stem 
which first gives off a large diarch trace and later an aphlebia trace (Fig. 9), to be followed by 
a monarch petiolar trace. This succession is shown also in Figs. 19, 20, and 21. Slides 407. 
24-25. x 20. 
Fig. 8 a is a high-power micrograph of the stem stele from Fig. 8 and is comparable with 
that shown in Fig. 2. x 95. 
Fig. 9 a is a high-power micrograph of the stem stele from Fig. 9, and shows the 
separation of an aphlebia trace ( aph .) and origin of a monarch petiolar trace, while the rest of the 
stem stele is preparing for the emission of roots. This series should be compared with that shown 
in Figs. 19 and 20, and with Fig. 21. x 95. 
PLATE LXXXII. 
(Figs. 10-18.) 
Fig. 10. An obliquely longitudinal section through a stem bearing a small petiole with its 
aphlebia ( aph .). In the upper part of the section can be seen a large leaf-trace in its attached part. 
Slide 416. 4. x 20. 
Figs. 11-13 represent three sections from a series through a stem bearing at first a diarch 
trace and later roots. Slides 417. 2-5. x 30. 
Figs. 11 a, 12 a, and 13 a are high-power micrographs of the respective stem steles, x 95. 
The series shows diagrammatically the change in character of the stem as it passes from 
a purely leaf-bearing zone into a root-bearing zone, and should be compared with Figs. 1-4. 
Fig. 11 a. shows the duplicated protoxylem of the stem which is characteristic of intemodal 
structure, and corresponds with that shown in Figs. 2 and 8 a. 
Fig. 12 a shows the rapid increase in diameter of the stele in preparation for root formation 
and pseudo-secondary (p.s.) development of new metaxylem. 
Fig. 13 a shows a stem section in marked contrast to such a one as is shown in Figs. 1, 2, 
8 a, and 11 a. It may be regarded as bearing some resemblance to the stem of Diplolabis Rtimeri 
and Metaclepsydropsis duplex ; The bulk of the tracheides have a small diameter. 
Figs. 14 and 15 represent two sections from the same series. Slides 393. 26 and 28. 
Fig. 14 shows a monarch trace entering the base of the petiole and the stem in a root¬ 
bearing phase. AX. px. can be seen the protoxylem of the aphlebia trace. Cf. Text-fig. 1. (Roots 
were numerous in the next section, 393. 25.) Slide 393. 26. x 20. 
Fig. 14 is a high-power micrograph of the node from which the above monarch trace took 
its origin. It shows the single protoxylem group characteristic of a purely leaf-bearing node 
(vide Fig. 1) and the addition of new primary xylem by pseudo-secondary formation. Slide 393. 28. 
x 95 - 
Fig. 16 is a high-pawer micrograph of the adaxial part of a diarch petiolar bundle. The 
minute cusps with intervening protoxylem elements can be clearly seen. The phloem elements are 
as usual badly preserved. This figure should be compared with the branching diarch petiole seen 
in Fig. 24. Slide 320. 11. x 95. 
Fig. 17 is a high-power micrograph of part of a group of four ‘ Botryopteridean 1 sporangia 
measuring on an average 275 n across. Slide 326. 2. x 95. 
Fig. 18. A single larger ‘Botryopteridean’ sporange represented at the same magnification 
as those of Fig. 17. Such sporangia occur in all the three blocks from which the specimens 
figured have been obtained. Slide 400. x. x 95. 
PLATE LXXXII 1 . 
(Figs. 19-24.) 
Figs. 19 and 20 are micrographs of two successive sections of a stem at a node. The leaf- 
trace which is just becoming free in Fig. 19 is shown as the petiole bundle in Fig. 20, and the 
small aphlebia trace ( aphd .) not yet detached from the stem stele in Fig. 19 is now (in Fig. 20) 
found passing into the base of an aphlebia. 
