JOURNAL OF MICROSCOPICAL SCIENCE. 



EXPLANATION OP PLATES XXXII & XXXIII, 



Illustrating Mr. F. O. Bower's Memoir " On the FurtLe. 

 Development of Welwitschia mirabilis.'' 



Key to Lettering, 

 ap. = apex of stem. I. c. = lobe of crown, pi. I. = plumular leaf. 

 (f = male branch, pr. xy, = protoxylem. /;;•. ph. = protophloeiu. 

 *'. d. =: soft bast. Ao. = secondary bundles, int. dun. = intercalated 

 bundle, per. ser. = peripheral series. ep. = epidermis, sp. c. = 

 spicular cell. scl./. = sclereuchyma fibre, ck. = cork. ck. cb. = 

 cork cambium, liy. w. = lignilied wall. eel. w. = cellulose wall. 



Fig. I. — X y°. Transverse sections of the root of the youngest plant 

 in the Kew collections, at a distance of about six inches below the feeder. 



Fig. II. — X Y. i, ii, iii, transverse section of the same root higher 

 up, showing the connection of the secondary bundles (^j) with the central 

 plate of vascular tissue. 



Fig. III. — i, ii, natural size. External view (i, lateral; ii, apical) of the 

 plant from which the sections figured below (Figs, iv, vi, viii — x) were 

 taken. The dotted lines, 1 — 6, show the points at which the sections 

 1 — 6, Fig. VI, were taken. Those marked a, b, show the position of the 

 planes of section of Fig. viii, a and b. The root continued for a distance 

 of nine inches beyond tliat represented in this figure, and was there broken 

 off short. 



I'iG. IV. — X \°. Transverse section of the root of the above plant, at 

 a point about six inches below the swelling. Besides the stellate central 

 group of vascular bundles, a peripheral series is here to be seen. Tiic 

 sign ( X ) indicates gum passages. 



Fig. V. — X if^. Transverse section of the peripheral part of an old 

 root (about one inch in diameter), showing the origin of three vascular 

 bundles ; the arrow points towards the centre of the root. 



Fig. VI. — (1 — 6) x f- Series of transverse sections, taken at points 

 marked 1 — 6 in Fig. iii, (see text). No 7 (x Y), part of such a section 

 as No. 6, showing the intercalation of a fre.-h bundle between the older 

 bundles of the leaf trace. 



Fig. VII. — x ^Y*. Transverse section at the apex of a seedling four 

 months old, showing externally the base of the cotyledons, within these 

 the two plumular leaves (pi.), and between the latter the apical cone (ap.). 

 Laterally to this, the two lobes of the crown (/. c). 



Fig. viii. — X f. a, b, longitudinal sections in planes marked in Fig. iii, 

 A, B. In A, the lines of shading are intended to indicate the arrangement 

 of the tissues, (cf. text). The area ( X ) is represented under a higher power 

 in Fig. X. In B, the dotted line indicates the relative position of Fig. vi, 6. 



