142 Dr. J. S. B. Sanderson on the supposed 



R. Alaternus, latifoUa, cathartica, &c. The last- mentioned was 

 selected for examination as most suitable. 



1 . Arrangement and development of parts forming the leaf-bud. 

 — The leaf-buds were examined at two periods, — first, in the 

 middle of last January, and afterwards early in April, when 

 nearly ready to open. The internal parts are protected by a 

 resistent tegument, composed of scales of a brown colour and 

 horny consistence. Each of these scales presents a modified 

 form, not of the leaf, as is most commonly the case, but of the 

 stipule ; or rather, to speak more accurately, each scale corre- 

 sponds to a combination of the two stipules which belong to one 

 leaf. The arrangement of the scales is imbricated, each scale 

 covering all its successors by both its margins. The rudimentary 

 leaves are arranged in pairs, which alternate with each other ; 

 the two leaves forming each pair being opposite and of nearly 

 equal size. The four stipules of the last pair of leaves (viz. the 

 pair most distant from the axis) are enclosed in the first pair of 

 tegumentary scales, while they, on the other hand, enclose the 

 four stipules of the penultimate pair of leaves, and so on to the 

 centre of the leaf-bud ; an arrangement that illustrates in a beau- 

 tiful manner the correspondence between the scales and the 

 stipules. Frequently the scales of the first pair are bifid, thus 

 manifesting a tendency to division into two symmetrical organs. 

 The vernation of the rudimentary leaves is convolute ; the sti- 

 pules occupying the space intervening between the convexities 

 of their rounded folds. 



Structure and development of the rudimentary leaves and sti- 

 pules. — In its earliest condition the leaf is nothing more than 

 a lateral budding out of the axis, which soon becomes compressed 

 from behind forwards *. In a stage slightly more advanced, it is 

 an awl-shaped organ, the lateral margins of which are curved in- 

 wards and forwards ; it is inserted into the axis by an expanded 

 base. In this condition the stipules are seen as two flattened 

 projections, one on each side (PI. III. A. fig. 1 a) . Still later, as in 

 fig. I by the involution of the margin of the leaf is more com- 

 plete, and the stipules have lost their rounded form, having be- 

 come somewhat spatula-shaped organs, — much broader, however, 

 below than above. In this state both leaf and stipule consist 

 entirely of cylindrical cells, the greatest diameter of which is 

 about 0*009 millim. The breadth of the leaf now diminishes 

 considerably in proportion to its length, a result which is pro- 

 duced by the continued involution of its margins. The con- 



* The terms anterior and posterior, right and left, internal and external, 

 &c., are usual in relation to the leaf» taken by itself; its future upper surface 

 being considered as anterior, as it is by it that it looks towards the axis. 



