Antheridia of Rhamnus. 143 



vexities of the rounded folds are seen on its anterior aspect to 

 form two undulating ridges, one on each side of a median fur- 

 row. In the mean time the stipule, originally a mere lateral 

 projection from the base of the leaf, has increased in relative 

 size, and now equals or exceeds the leaf itself. A difference of 

 size is also observed between the two stipules belonging to the 

 same leaf, the right one from the first somewhat exceeding its 

 fellow. After they have arrived at about one-eighth of their 

 ultimate length, both are furnished with a linear median thick- 

 ening, which extends from the base to the apex. The space 

 intervening between this thickening and the margin is greater 

 on the side next the leaf than on the opposite, as a result of 

 which, the margin itself is convex on the one side, while on 

 the other it is nearly rectilinear. Those of the outer stipules of 

 the leaf-bud, which have assumed the character of protective 

 scales, are brown and horny at their upper part, and much 

 broader in proportion to their length than the rest (fig. 1 /). 



Origin and development of the so-called Corynidia. — The cory- 

 nidia are found only in stipules which have arrived at about one- 

 eighth of the length of the whole bud, those of smaller size pre- 

 senting no trace of their existence. They originate from the 

 median thickening of the stipule, as nipple-shaped buddings-out 

 of the anterior surface (fig. 2 a). Soon they assume a clavate 

 form and overhang the inner margin of the stipule, appearing in 

 the interval between this organ and the leaf (fig. 2 b). Each 

 consists of a central column of cellular tissue surrounded by a 

 simple layer of others, which do not differ in any respect from 

 those which surround them, and form the superficial layer of 

 the stipule. On the more external stipules of the leaf-bud, the 

 corynidia are found to have altered their form, having become 

 flask-shaped (fig. 2 b). It is difficult to determine whether the 

 enlarged extremity is occupied by a cavity containing a trans- 

 parent fluid, or simply by a lax cellular tissue. It is, however, 

 certain, that if such a cavity exists, it is not limited in any 

 distinct manner. 



At this point the development of the corynidia ceases, and 

 they soon become marcescent ; the upper part of the corynidium 

 shrinking into a mass of irregular form and dark brown colour, 

 which, after remaining for a time attached to the stipule by a 

 slender pedicle, eventually separates. In examining the leaf-bud, 

 there are always to be found a number of such masses floating 

 free in the water used for dissection. On pressing them between 

 two glasses, they are found to be solid, resistent bodies. When 

 sufficient force is used to disintegrate them, they are resolved 

 into a number of grains of irregular form, which for the most 

 part correspond in size to the cells of which the corynidia were 



