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EXPLANATION OF PLATE XXXIX. 
Illustrating Miss Ford’s paper on Psilotum triquetrum. 
Fig. 1. Transverse section of an aerial shoot of Psilotum below a bifurcation. st= stomata, 
pa = outer assimilating layer of parenchyma, scl— sclerenchymatous zone, p) d — inner parenchymatous 
zone, n = siliceous nodules, /.v = protoxylem, .r = xylem, ph = phloem, f= central fibres, and p> x’ = 
secondary protoxylem. x 34. 
Fig. 2. Transverse section of portion of aerial stem, showing lignification of phloem tissue, px — 
protoxylem, st = phloem tissue, en — endodermis. x 250. 
Fig. 3. Assimilating cells from the outer cortex in longitudinal view. x 150. 
Fig. 4. Longitudinal section of phloem tissue from an aerial shoot. st= sieve-tubes, pa = paren- 
chyma, m = globular deeply staining masses of substance, x 300. 
Fig. 5. Longitudinal section of a leaf of Psilotum. x 40. 
Fig. 6. Transverse section of the apex of an aerial shoot, showing the apical cell, x 300. 
Fig. 7. Longitudinal section of the same, x 300. 
Fig. 8. Part of a transverse section of an underground stem of Psilotum. e 7 i = endodermis, ph = 
phloem tissue. 
Fig. 9. Transverse section of a branch nearer the apex, x 195. 
Fig. 10. Transverse section of a branch below bifurcation, x 180. 
Fig. 11. Ditto, but near the apex and showing tracheids passing off to a lateral bud /. x 173. 
Fig. 12. Transverse section below the apex of an underground branch, showing a single lignified 
tracheid. x 215. 
Fig. 13. Transverse section of the intermediate portion of the aerial stem. ph ==- phloem tissue, 
A' 2 = secondary xylem, pa = central parenchyma, / = single central tracheid. At g the break in the 
xylem ring is seen, x 90. 
Fig. 14. Ditto, higher up. en = endodermis, /= central fibres, x 42, 
T t 2 
