54 



MANUAL or BOTANY 



The Hypopodium or Leaf-base.— This is often very difficult 

 to distinguish from the stem. The tissues of both are con- 

 tinuous, and unless some outward peculiarity appears the two 

 cannot accurately be delimited. Very often, however, the point 

 of union of the two is marked by a swelling of the hypopodium 

 forming a sort of cushion called a pulvinus, and in some cases 

 it appears as a definite articulation. When the leaf-base is 

 broad, this swelling extends for a considerable distance round 

 the stem. Such leaves can be detached very readily and leave 

 a kind of scar which can be noticed on the stem after the leaf 



Fig. 81. 



Fig. 82. 



Fig, 81. Decurrent leaves of the Comfrey. Fig. 82. A portion of a brancli, 



r, of the commou Rose {Eosa canina). a. A prickle. 6. Bud in the axil 

 of a compound leaf, /, with stalked leaflets, p. Petiole. *, s. Adnate or 

 adherent stipules. 



has fallen off {fig. 37). This cushion may form a kind of 

 sheath, almost embracing the stem, as in the common 

 Pelargonium. It may be somewhat membranous and com- 

 pletely encircle the stem, as in the Fool's Parsley {fig. 78). 

 These modes of arrangement are known as semi-amplexicaul 

 and amplexicaul, respectively. In some plants the leaf-base is 

 prolonged down the stem as a winged expansion, as in some 

 Thistles, when it is said to be decurrent {figs. 80 and 81). 



Frequently the leaf-base bears a pair of lateral branches, 

 which often become winged like the epipodium, but may assume 

 other forms. These are known as stipules. They have the 

 same structure as the blades of leaves, and are liable to similar 



