i8o 
Scott .« — Ipomoea versicolor , Meissn . 
EXPLANATION OF THE FIGURES IN PLATES 
XII and XIII. 
Illustrating Dr. D. H. Scott’s paper on Ipomoea versicolor , Meissn. 
The following lettering is used throughout the microscopical figures : — 
c 1 = normal cambium. 
pie- — normal external phloem. 
//z 2 = medullary phloem. 
ph z = interxylary phloem. 
px = proto xylem. 
x i = primary xylem. 
x 2 = secondary xylem. 
P — pith* 
£ = endodermis. 
Fig. i. Seedling, showing the whole plant, with the cotyledons and the first 
few leaves. G-G level of the ground. The upper internodes are already twining 
round a support. b, and c, positions at which the sections shown in Figs. 3, 4, 
and 5 were taken. Two-thirds of natural size. 
Fig. 2. Semi-diagrammatic transverse section of the hypocotyl. C-C median 
plane of the cotyledons. red— primary xylem of the cotyledonary traces. 
yellow — secondary xylem. blue = phloem, medullary, interxylary, and external. 
brown = periderm. The parenchyma is left white. 
Fig. 3. Part of a transverse section taken at a (Fig. 1). A pair of cotyledonary 
bundles is shown, with converging protoxylem, and a common group of medullary 
phloem just within them. 
Fig. 4. Corresponding section much lower down, at b (Fig. 1). The xylem- 
groups are now united with outwardly-directed protoxylem. The medullary 
phloem is passing to the exterior, forming two strands, one on either side of the 
xylem-plate. The whole has been enclosed by secondary wood. 
Fig- 5 - Corresponding section somewhat lower, at c (Fig. 1). The medullary 
phloem now lies to the outside of the xylem-plate. Observe that the cambium is 
here beginning to form a medullary ray. 
Fig. 6. From a much older hypocotyl, showing a parenchymatous ‘island’ with 
interxylary phloem, in course of development. The cambium is beginning to form 
new wood and thus complete the formation of the island. 
Fig. 7. From the same hypocotyl as Fig. 6, showing a similar island completely 
imbedded in the wood, and containing much interxylary phloem. The arrow c x 
points towards the cambium. 
Figs. 3-7 are X330 diam. 
