104 MR. O. BENTHAM OX MYKTACEiE. 



individual, grows out of or proceeds from a preexisting one, of wlucli 

 at first it forms a part. And as, in tlie case of animals as well as 

 plants, it is not always easy to determine the precise moment 

 when the offspring becomes a separate individual, so, before sepa- 

 ration, it is as difficult to fix the precise point marking the com- 

 mencement of each separate organ, 



2. In vegetable homology, the perfect phsenogamous plant con- 

 sists of an axis and of appendages^ often called leaves, in a theo- 

 retical sense— but which it is more convenient to term leaf organSy 

 to distinguish this general meaning from that special modification 

 to which more usually the name of leaf is restricted. These leaf 

 organs, under all the variations which distinguish the bud-scale, 

 the leaf, the bract, the sepal, the petal, the stamen, and the carpel, 

 yet agree in their general characters as to origin or insertion, de- 

 velopment and ultimate separation from the axis. And in all 

 leaf organs we include in the organ the stalk supporting the la- 

 mina — the petiole of the leaf, the filament of the stamen, &c. 



In considering, therefore, whether the outer cup, which encloses 

 or is adnate to the ovary in Myrtacese, should be described as 

 part of the peduncle (i. e, of the axis), or as part of the calyx, or 

 as an independent organ — in determining whether the calyx com- 

 mences at its base or at its apex, we should compare it not only 

 with the corresponding organ in allied Natural Orders, but also 

 with the corresponding portion of other leaf organs. 



In the great majority of cases we have no hesitation in fixing 

 the point Vvhere the leaf organ commences. Ultimate separation 

 by disarticulation or decay takes place at the point where it di- 

 verges from the stem, peduncle, or receptacle, so that in fallmg 

 off it leaves only a scar or slight protuberance or concavity. But 

 in all leaf organs, whether vegetable or floral, there are exceptions 

 which have not always been uniformly dealt with. 



In the leaf the lower portion of the petiole persists as a spine 

 in Sarcocaulorij or hook in some species o^ Comh^etum and Sniuf^^j 

 or the whole rhachis in many Astragali and other pinnate-leaved 

 plants of dry hot countries forms a persistent spine ; or, in other 

 leaf organs, a portion of the base of the corolla-tube in Nuxifij 

 Dampiera, and others, or of the filaments of the stamens in Btylo- 

 lasium, Leeostenion^ &c., or of the carpels in circumsciss capsules, 

 remains also persistent after disarticulation of the remainder. In 

 all these cases we uniformly describe these persistent portions as 

 belonging to the leaf organ, not to the axis ; the line of demarca- 

 tion is at the point of divergence, not at the point of disarticulation- 



