SHOWING STRUCTURE, FROM THE RHYNIE CHERT BED, ABERDEENSHIRE. 679 
Fig. 84. Transverse section of stem with a branch-trace ( br . tr.) on its way out through the cortex, 
x 14. (No. 2502.) 
Fig. 85. Transverse section of large stem with a branch-trace (br. tr.) just emerging from the cortex, 
x 14. (No. 2459.) 
Fig. 86. Next section of the same showing the branch ( B ) still connected with the stem, x 14. 
(No. 2461.) 
Fig. 87. Next section of the small branch, the xylem of which has now become typically stellate, 
x 14. (No. 2492.) 
Fig. 88. Transverse section of stem showing a small branch ( B ) connected to it by a narrow web of cortex, 
x 14. (No. 2503.) 
Fig. 89. Transverse section showing two steles (a and b) with imperfectly stellate xylem, enclosed in the 
same cortex, x 14. (No. 2459.) 
Plate XII. 
Fig. 90. Transverse section of stem surrounded by the free portions of leaves and bearing a small leafy, 
lateral branch cut longitudinally. x 14. (No. 2478.) 
Fig. 91. Stem cut transversely and departing branch ( B ) cut longitudinally. X f I\. (No. 2470.) 
Fig. 92. Further portion of the branch in fig. 91 showing the stele and leaf-traces. x 20. (No. 2470.) 
Fig. 93. Tangential longitudinal section of the cortex of a stem shewing in continuity with it a branch in 
transverse section with a stele like that of the larger rhizomes, ph., phloem of branch ; x., xylem of branch, 
x 14. (No. 2470.) 
Fig. 94. Transverse section of branch-stele in the cortex of a stem. The strand of xylem is surrounded 
by the collapsed phloem. x 33. (No. 2504.) 
Plate XIII. 
Fig. 95. Stem with the structure of the advanced transition region with a small lateral branch still 
attached, x 12. (No. 2477.) 
Fig. 96. Large stem of typical structure surrounded by transverse sections of leaves. The stellate xylem 
of the stele is double as if in preparation for dichotomous branching. x 14. (No. 2479.) 
Plate XIY. 
Fig. 97. Transverse section of a stem showing the preparation for the departure of a branch-trace (br. tr.) 
from one arm of the stellate xylem. x 7|-. (No. 2505.) 
Fig. 98. Transverse section of the same stem at a higher level. The branch-trace (br. tr.) has increased 
in size where it lies in the neighbourhood of the parent stele. Adjacent to the main stem, but not in 
connection with it, the branch is cut where it is dividing into two (Ba, Bb). x 7-|. (No. 2506.) 
Fig. 99. Transverse section of the same stem at a still higher level. The stele of the branch (br. tr.) is 
cut on its way out through the cortex of the main stem, and two steles (Ba, Bb) are contained in the cortex 
of the further portion of the branch, which is bent back. x 7J. (No. 2507.) 
Fig. 100. The stem in fig. 98 more highly magnified, c., cortex of main stem ; en., layer in position of 
an endodermis limiting the stele of the main stem; c. br., cortex of branch; X, discontinuity between the 
cortical tissues of the emerging branch and of the main stem. x 14. (No. 2506.) 
Fig. 101. Region of discontinuity between the cortex of the main stem and of the branch in fig. 100 more 
highly magnified, c., cortex of main stem; c. br., cortex of branch. x 33. (No. 2506.) 
Plate XV. 
Fig. 102. Portion of a section of the silicified peat of the block found by Dr Gordon. A large stem of 
Asteroxylon is seen above, below there are smaller stems, while the track of a rhizome is traceable across the 
peat formed of the small peculiar axes. x 14. (No. 2505.) 
TRANS. ROY. SOC. EDIN., VOL. LII, PART III (NO. 26). 
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