McNicol. — On Cavity Parenchyma and Tyloses in Ferns. <113 
EXPLANATION OF PLATE XXV. 
Illustrating Miss McNicol’s Paper on Cavity Parenchyma and Tyloses. 
Fig. 1. Microlepia platyphylla. Trans, sec. of part of petiolar bundle, en, endodermis 
p, pericycle ; ph , phloem ; xy, xylem ; cp , cavity parenchyma. 
Fig. 2. Pteris aquilina. Long. sec. of petiole showing cavity parenchyma. 
Fig. 3. The same. Beginning of formation of cavity parenchyma by tylose-like intrusions iy 
into the spiral vessels px. mx, metaxylem ; px 1 , remains of spiral vessels ; n, nucleus. 
Fig. 4. The same. Later stage in the formation of cavity parenchyma. 
Fig. 5. The same. Trans, sec. of petiole, con. p., conjunctive parenchyma. 
Fig. 6. Alsophila excelsa. Petiole, long. sec. showing cavity parenchyma. 
Fig. 7. Dicksonia antarcticci. Petiole, long. sec. showing cavity parenchyma. 
Fig. 8. Cibotium princeps. Trans, sec. of a single ‘ bay’ in the vascular bundle of the petiole. 
xs, xylem sheath ; /, reticulately lignified tracheid. 
Fig. 9. The same. Enlarged view of strand of cp . px 1 , the remains of a disintegrated spiral 
vessel. 
Fig. 10. The same. Long. sec. of a strand of cavity parenchyma, et, elongated tracheid. 
Fig. 11. Helminthostachys. Semidiagrammatic view of trans. sec. of sterile leaf-stalk. 
Fig. 12. The same. Long. sec. showing cp. bp , tracheids with bordered pits. 
Fig. 13. Angiopteris evecta. A single petiolar bundle, sc, secretory cells. 
Fig. 14. Marsilia quadrifolia. Bundle of petiole, trans. sec. 
Fig. 15. Marsilia quadrifolia. Cavity parenchyma enlarged, e, cavity. 
Fig. 16. Marsilia quadrifolia. Long. sec. of cavity parenchyma. 
Fig. 17. Loxsoma. Cells of cavity parenchyma — after G wynne- Vaughan. 
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