Trees; a handbook of forest-botany for the woodlands and the laboratory . d palmate venations merge one into theother, are afforded by the Lime and the Plane. In theformer (Fig. 21) we see that while the predominant typeis clearly pinnate, there are two or three basal secondarieswhich arise with the midrib at the base of the leaf anddiverge at different angles, throwing out strong outerbranches so that the venation of this leaf is almostpalmate below. It may be appropriately described aspinnate with the base pseudo-palmate. In the Plane, again (Fig. 22), while the venation ap-pears obviously p
Trees; a handbook of forest-botany for the woodlands and the laboratory . d palmate venations merge one into theother, are afforded by the Lime and the Plane. In theformer (Fig. 21) we see that while the predominant typeis clearly pinnate, there are two or three basal secondarieswhich arise with the midrib at the base of the leaf anddiverge at different angles, throwing out strong outerbranches so that the venation of this leaf is almostpalmate below. It may be appropriately described aspinnate with the base pseudo-palmate. In the Plane, again (Fig. 22), while the venation ap-pears obviously palmate at first sight, the two stronglateral ribs diverge from the midrib some little way abovethe junction with the petiole, and are, strictly speaking,merely the lower secondaries of a pinnate examples of the same kind are to be met within Populus alba, the Birch and elsewhere, and may bereferred to as pseudo-palmate. v] PSEUDO-PALMATE VENATION 63 The following afford examples of pseudo-palmatevenation :— Guelder RoseMulberry Ivy Hawthorn Fig. 22. Leaf of Plane, Platanus orientalis, showing pseudo-palmatevenation. If compared with the Norway Maple (Fig. 15) it will be seenthat the basal primaries do not originate strictly from the same pointwith the midrib (Ett). The following afford examples of pinnate venationwith pseudo-palmate base:— Travellers Joy Service Tree Abele Grey Poplar Hawthorn Ivy Lime Aspen Black Poplar. 64 PALMATE VENATION [CH. In typically palmate venation all the principal ribsbehave as primaries and must be regarded as primaries arise, together with the midrib, fromone point at the base of the leaf where it joins thepetiole, and diverge thence in a radiating manner, as iswell seen in the Norway Maple (Fig. 15). The following afford good examples of true palmatevenation:— Maple Sycamore Norway Maple Black Currant Ivy Gooseberry Vine Red Currant Fig.
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