THE LEAF 
Si 
tion (Magnolia), or be represented by tendrils (Smilax), 
thorns (Acacia, Paliurus, &c.), hairs (Anacampseros), and 
so on. 
Descriptive Terms. The student should practise describing leafy 
shoots until expert in handling the terminology, but there is no need 
to commit the terms to memory. At first he should describe in detail 
in the order given below, but afterwards he should try to render his 
descriptions short and pithy without sacrifice of essentials ; this of course 
can only be well done by comparison with related forms to see what 
points are common to all. 
Leaves as to phyllotaxy (above) may be radical , or on the subaerial 
stem ( cauline ) ; whorled (verticil late), opposite (and then decussate if each 
pair is at right angles to the next, connate if the two are concrescent as 
in Lonicera, anisophyllous if unequal in size or shape), or alternate (the 
phyllotaxy fraction may be given, or the number of ranks described by 
the terms di-, tri-stichous , &c.). With regard to its insertion or mode of 
union with the stem the leaf may be petiolate or sessile (i.e. with or 
without stalk respectively; the petiole is described like a stem), auricled 
(with two lobes of the blade overlapping the stem), a?nplexicatil (the 
lobes clasping the stem), sheathing (as in Grasses, the leaf-base forming 
a tube round the stem), perfoliate (the leaf united round the stem, as in 
Bupleurum), decurrent (continued by a wing on the stem, as in thistles), 
&c. It may bear a ligule or scale at the upper end of the leaf-base or 
sheath, as in Grasses. It may be stipulate or exstipulate (with or without 
stipules respectively) ; the shape, &c. of the stipules is described as if 
they were leaves, and they may be free or adnate (F in fig. 3; concrescent 
with the leaf-base or petiole, as in rose), united to other stipules, inter - 
or intra-petiolar , branched, &c. (see Rubiaceae), ochreate (sheathing, as 
in Polygonaceae), or modified in various ways (above). The venation 
(arrangement of the veins) may be pinnate or palmate ; in the former 
case there is a midrib with lateral veins branching from it, in the latter 
several equal veins spread out in the leaf like the ribs of a fan, from one 
point. The further ramification of the veins is described by the terms 
net-veined (irregular meshwork, as in most Dicotyledons), parallel-veined 
(meshes more or less rectangular, as in most Monocotyledons ), fork-veined 
(veins forking into two, as in Ferns). 
Leaves are divided into simple and compound, according as the stalk 
bears one or several separate leaflets. In the latter case the leaflet is 
described as if it were a leaf, and the common stalk is often called the 
rachis. If the leaflets spring from the sides of the rachis, as in the pea, 
the leaf is pinnate (F), if all from one point palmate (E). If the leaflets 
of a pinnate leaf, as in many Acacias, are again pinnately compound, 
the leaf is bipinnate. A leaf with 3 leaflets (as in clover) is ternate or 
tri-foliolate , with 3 ternate leaflets biternate. Pinnate leaves may be 
equally (pari-) pinnate (with an even number of leaflets), unequally 
(impari-) pinnate (with an odd leaflet at the end), or interruptedly 
pinnate (large and small leaflets alternately as in many Rosaceae). A 
palmate leaf with 5 or 7 leaflets is often called digitate. The leaflet may 
have stipule-like organs, or stipels (adjective stipellate). 
4—2 
