280 



HUTCHINSON'S POPULAR BOTANY 



If, as is generally agreed, the trumpet-shaped portion of the leaves of 

 Sarracenia is really an expansion of the petiole, it would be botanically 

 described as a pkyllode, and thus would answer to the leafy expansion of the 

 petiole of certain Australian species of Acacia as, for instance, Acacia, 

 melanoxylon, which, when young, possesses bipinnate leaves with flattened 

 petioles, but which are succeeded by others more phyllode-like as the plant 

 grows older, until at last the leaflets (pinnce] entirely disappear, and phyl- 

 lodes only are produced. The phyllodes have the appearance, and per- 

 form all the functions, of normally developed foliage-leaves. 



There is a tendency among the Acacias, as well as some closely allied 



plants, to develop different forms 

 of leaf on the same individual with 

 a capriciousness that is extra- 

 ordinary. Not only will you find 

 pinnate, bipinnate, and tripinnate 

 leaves en the one plant, but in- 

 stances are not uncommon in 

 which a single leaf inclines to all 

 these forms at once. The leaf of 

 the Honey-locust-tree (Gleditschia 

 triacanthos) is a case in point (fig. 

 342). The tree is a native of 

 North America, where its long 

 thorny branches wage incessant 

 war with the unarmed Maple- 

 trees, in close proximity to which 

 it is usually found growing. 

 Surely if plants, like animals, are 

 liable to be affected by changes of 

 the moon, the Honey-locust-tree 

 has fallen under the baneful in- 

 fluence ! It reminds one of those 

 old Lime-trees (Tilia platyphyllos) 

 mentioned by Dr. Burnett, .which, instead of developing the cordate or 

 obliquely cordate leaves of this species, regularly put forth leaves of a 

 hooded (cucullate) form. These trees were growing in the churchyard of 

 Seidlitz, in Bohemia, seventy years ; ago possibly they are still growing 

 there. In Burnett's time the peasants affirmed that the production of 

 the hooded leaves was due to the fact that some monks from a neigh- 

 bouring convent had been hanged on the trees ! 



Those who have what Americans would call " a big swallow " may be 

 satisfied with this explanation, but the diversity of form in the normally 

 heterophyllous leaves of Gleditschia triacanihos, Acacia heterophylla, etc., has 

 no such convenient story to account for it, nor are we in a position to suggest 



FIG. 342. HETEROPHYLLOUS LEAF OF HONEY- 

 LOCUST-TREE. 



Some of the leaflets are entire, others broken up in various 

 degrees into smaller leaflets. 



