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( 27 ) 
PHYLLOTAXIS. 
As the buds grow from the axils of the leaves, their arrangement is the 
same as that of the leaves. They are either opposite or alternate. 
When the buds are opposite, one pair stands transversely to the next 
lower, so that, when seen from above, the four buds form a cross, as do also 
the leaves and the branchlets ; the third pair corresponds to the first one. 
This position is called decussate, and we find it in the species of Euonymus, 
Staphylea, Aesculus, Acer, Negundo; Hydrangea, Cornus (except C. alter- 
nifolius), Loniceraf, Sambucus, Viburnum, Bignonia, Tecoma, Fraxinus, 
Foresteria. 
A whorl of three buds we find in Catalpa, and also usually in Cephal- 
anthus (sometimes four or only two). Each whorl alternates with the next 
one, so that, seen from above, a whorl of six is formed. In all the rest of 
our woody plants the buds are alternate. Though seemingly irregular they 
are arranged in a definite order. The buds are alternate in two lines 
(bifarious), or in other words the third bud corresponds to the first, th-e 
second to the fourth ; two buds make one circuit, and this is expressed by 
the fraction \ ; the numerator indicates the circuit, the denominator the 
number of buds. This arrangement we find in the species of Asimina, 
Vitis, Ampelopsis, Cercis, Hamamelis, Brunnichia, Dirca, Ulmus, Celtis, 
Morus and Smilax. 
In Betula and Alnus three buds make one circuit in a spiral line ; the 
fourth bud stands above the first (£ 
In the majority of our woody plants five buds make two turns in a spiral 
line, and the sixth bud stands above the first (two-fifths). In the oaks the 
upper buds are somewhat crowded. The beech and Tilia, though properly 
belonging here, have the buds on the horizontal branches in two oppo- 
site lines. 
There is one little tree ( Ptelea ) with eight buds in three circuits (f), 
and one shrub (Amorpha fruticosa), with thirteen buds in five circuits (five- 
thirteenths). In Bhamnus four buds make one circuit, but the merithalls* 
between the first and second and the third and fourth, are much shorter than 
between the second and third ; and as we sometimes find the pairs of buds 
in Euonymus and Fraxinus displaced (one higher than the other), we may 
concede that Rhamnus belongs to the same division as those. The position 
is properly decussate. The same conclusion we may make in regard to the 
elm, the seedling of which has opposite leaves ; and perhaps we may ex- 
plain the bifarious position of the buds on the branches by a (hypothetic) 
torsion of the merithalls. 
The best way to count the buds and their circuits, is to thrust a pin 
into each leaf-scar at a right angle to the stem, and attaching a thread 
to it, pass this from the lower to the next higher until the one is reached 
which corresponds to the first one. 
Figures 18 — 21 on PI. IV show in diagram the phyllotaxis of four 
different woody plants. The figures represent the bark split longitudinally 
*Intemodes. 
