1892.] The Identification of Trees in Winter. 181 
I. The determination of the phyllotaxy of the leaves of 
the species examined, as shown by the petiole-scars remain- 
ing from last year’s leaves, is the first step towards identifica- 
tion. It so happens that a classification of shrubs and trees 
into those with alternate, spiral, and opposite or whorled 
leaves gives rise to three fairly equal sets. The determina- 
tion of the phyllotaxy of a plant at once excludes quite a 
large list of shrubs and trees with another kind of arrange- 
ment of leaves from the list of possibilities. The rarer 
phyllotaxies such as 3 (Spirea opulifolia Linn., fig. 13); 2 
plant still more easy. In certain species the phyllotaxy is 
occasionally or even quite regularly (Castanea) more or less 
variable in different twigs of the same tree, but these cases 
are sufficiently rare not to give any serious difficulty. 
Il. The form of the more fully developed petiole-scars and 
the mode of disposition of the fibrovascular bundles where 
intersected at the petiole-scar is the second important 
means of classifying ligneous plants. The following are some 
of the most important types: : 
1. In those petiole-scars where the outline is markedly 
Tounded, the fibrovascular bundles are often arranged ina 
Sort of cj 
aren quinguefolia Michx., fig. 6; C. elastrus scandens Linn., 
g. 8; aromatica Ait., fig. 16; and Catglpa speciosa 
; etimes these bundles take the form rather of a 
“ircular area than of a circle. 
P 2. In those petiole-scars which have a broadly circular 
°rm below but a s 
dles are of 
atropur pu 
’ S 
Warder), Som 
‘orm several distinct sets in the same scar. 
us j 
h 
these bund] 
