KEY TO SUB-CLASSES, ORDERS AND GENERA. 185 
CVIII—BETULACE A!—cont. 
(i) Fruit a large nut, enclosed in a thick, cut and lobed, sometimes spines- 
cent involucre :— pe at B AF ete oe ... decelxxxix—Corylns, 
(ii) Fruit small, in drooping spikes, in the axil of large membranous reti- 
culated bracts :— ... 5 aa - at : decoxc—Carpinus, 
CIX—FAGACEAi— 
(I) Ovary 3-celled :-- 
(i) One female flower in each involucre ; nuts supported by a cup, or 
enclosed in an involucre not clothed with hard spines :— ... dcecexci-—Quercus, 
(ii) 2—4-female flowers (usually) in each inyolucre :— 
(1) Nuts enclosed in the enlarged involucre which is usually spinous :— 
decexciii—Castanopsis. 
(2) Nuts trigonous, enclosed in a 4-partite inyolucre of imbricating - 
bracts, not clothed with hard spines :—- ae se as decexciv--Fagus. 
(II) Ovary 6-celled ; three female flowers (csually) in each involucre; nuts 
enclosed in the large 2—4-valved spinous inyolucre :— __.. ... dcececxcii—Castanea, 
CX--SALICAE Ai— 
[Anatomical featwres-—Wood soft, medullary rays rarrow, vessels small, — 
uniformly distribnted, wood parenchyma not much developed, wood fibres wide, walls 
not thick, pits simple. } 
(I) Characters of the order (q.v. in the Synopsis) :— ge . decexcy—Salix, 
CXI—GNETACEAi— 
[Anatomical features——The general structure of the wood resembles that of 
normally built Dicotyledons. It consists of vessels, wood fibres, wood parenchyma, 
and medullary rays. No resin canals. Gnetum scandens, like many dicotyledonous 
climbers, shows on transverse section concentric bands of wedge-shaped masses 
of xylem and phliem, separated by medullary rays. | 
(1) Characters of the order (q.v. in the Synopsis) :— ... decexcvi—Gnetam, 
CXII—CONIFER A— 
| Anatomical features.—The trunk of Coniferous trees shows the same general 
arrangement of tissues which we find in normal Dicotyledons, but the wood is without 
vessels, hence, on the transverse section, without pores. 1t consists of medullary rays 
and of long thick walled tracheides, arranged in radial lines, with large bordered pits, 
usually on their radial walls only. In the earliest formed wood, contignous tc the 
pith, the tracheides have a spiral or annular thickening of their walls. The annual rings 
are distinctly marked by belis of very thick walled tracheides in the onter (autumn) 
wood, and of thinner walled tracheides in the spring wood of the succeeding year. 
Resin canals, lined by small thin walled secreting cells (as in Dipterocarps) are found 
in the leaves, the bark, and the wood; in the wood they are vertical among the 
tracheides, and horizontal in the medullary rays. | 
(1) Cones perfect ; seeds concealed by the scales of the cones :— 
(i) Scales of the cone few ; ovules erect; pollen grains not winged :— 
(1) Scales of cone opposite in several tiers :— 
(A) Scales of cone woody; seeds winged :— 
(a) Cones subglobose or short-oblong, of 6—12 scales, central pairs 
fertile; seeds with an orbicular wing; leaves scale-like, 
opposite (young, needle-like, 3-4-whorled ) :—-decexcvii—C upressus. 
(b) Cones subglobose or oblong of 6 (rarely 8) scales, innermost 
(rarely 2 innermost) pair fertile ; seeas with 2 unequal wings 
on margins; leaves minute, or scale-like, 3—4-whorled (young 
needle-like, short):— ... uae ee dcecx viii—Callitris, 
(c) Cones ovoid or oblong (rarely globose) of 6--12 scales with hook- 
ed tips, outermost pairs only fertile; seeds 2-winged ; leaves 
scale-like, in 4rows:— ... ae ude -. decexcix—Thuya, 
(B) Scales of cone succulent, forming a berry-like fruit; seeds not 
winged ; leaves either all linear and subulate, 3-whorled, or 
dimorphous consisting firstly of imbricate, opposite or decussate, 
scales, and secondly of subulate spreading leaves:— cm—J uniperus, 
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