THE LEAF. 



209 



3. ADNATION. 



1. Op Foliage-leaf to Stem. — A good example of 

 a normal adnation of this kind is afforded by the adult 

 foliage of the Cupressineas, in which the greater part 

 of the leaf, which is perfectly free in the juvenile 

 shoots, is- fused by its upper surface with the axis, 

 leaving only the tip free. It is simply this fact which 

 causes the striking difference between the two kinds 

 of foliage. Many winged stems owe their peculiarity 

 to fusion of the leaf -base with the axis. 



2. Of Foliage-leaf or Bract to Peduncle. — This 

 is not at all infrequent. Coster us and Smith mention 

 that in Carludovica palmata the leaf -stalk was fused at 

 the base for a certain length with the stalk of the 

 inflorescence. In a tulip recently seen, the uppermost 

 foliage-leaf, which was equal in size to those at a lower 

 level, was adnate laterally to the entire length of the 

 scape from the insertion of the leaf upwards. The 

 upper part of the leaf was similarly adnate to one of 

 the perianth-leaves. The whole formed a remarkable 

 abnormality. 



Normal cases of this abnormality, representing 

 probably mutational departures which have become 

 fixed in the life-history, are quite numerous. The 

 case of the lime is perhaps the best-known, where the 

 membranous bract becomes adnate for a certain dis- 

 tance with its axillary inflorescence-stalk for purposes 

 of seed-dispersal. In Monotropa Hypopiiys * and 

 Thesium ebractedtum* the same fusion occurs. In 

 Gongylocarpus rubricaulis* the inferior ovary becomes 

 fused both with its subtending bract and the main 

 axis. Then there are the instances afforded by the 

 epiphyllous flowers, e. g. Phyllonoma ruscifolia* Poly- 

 cardia lateralis* etc. In Erytliro chiton hypophyllan- 

 thus * the flower springs from the lower surface of 

 the leaf ; according to Planchon the flower- stalk in 

 this case is fused not only with the lower side of the 



* Of these the writer has seen herbarium material only. 

 VOL. I. 14 



