44 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
construction of the wood of the Beech, Oak, Walnut, and others, has a 
general resemblance; but if they are examined together it is seen, at a 
glance, to be entirely different. This difference is most marked in 
the tissues surrounding the vasa and bordering the medullary rays. 
An examination of a transverse section of timber by trans- 
mitted light shows that the concentric rings in an exogenous 
plant are not always representative of a year’s growth, nor is this 
notable feature confined to any particular family. The irregularity 
may be caused by chilling storms during the growing season, or 
by over-thinning the trees at the same period. The latter operation 
has a detrimental effect upon the production of timber, and an 
example of this is seen in the illustration of the Silver Fir (Fig. 2). 
It is there shown, that for several years after thinning took place, 
the tree made very little progress. 
Illustrations are also given of the wood of the Cedar (Fig. 3), 
Horse Chestnut (Fig. 10), Honeysuckle (Fig. 13), Pear Tree 
(Fig. 15), Theophrasta imperialis (Fig. 20), a tropical tree 
grown in a plant stove; Lime Tree (Fig. 21), and Whin 
(Fig 22), by way of comparison with those already mentioned, 
and to show the great difference that prevails in the structure of 
the wood between closely allied genera and species, as well as in 
those further apart in the natural system. 
The following is an alphabetical list of the Sections of Woods, 
in the same order in which they are numbered in the Cabinet of 
Micro-Lantern Slides which accompanies this report :— 
. Abies alba, 19. Amygdalus persica. 
. Abies Albertiana. 20. Andromeda floribunda. 
. Abies canadensis. 21, Araucaria imbricata. 
Abies Donglasii. 22. Ash root. 
. Abies excelsa. 23. Azalea pontica. 
. Abies Menziesii. 24. Beech root. 
. Abies morinda. | 25. Berberis dulcis. 
. Abies Nordmanniana. 26. Betula alba. 
. Abies pectinata. 27. Biota orientalis. 
. Abies Pinsapo. 28. Birch root. 
. Acacia Riceana, 29. Buxus arborescens. 
. Acer campestre, 30. Camellia japonica. 
. Acer platanoides. 31. Carpinus Betulus. 
. Acer Psendo-Platanus. 32. Carya alba. 
. Aisculus Hippocastanum. 
. Ailantus glandulosa. 
3. Castanea vesca. 
. Cedrus atlantica. 
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17. Alder root. 35. Cedrus Deodara, 
18, Alnus glutinosa. 36, Cedrus Libani, 
