8 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



in the earlier stages being almost indistinguishable. The 

 stamen is invested with envelopes which seem to corre- 

 spond to the outer integuments of the ovule and possibly 

 the carpel. A further discussion of these points, however, 

 must be left for the present. 



I. The Growing-Point of the Stem. 



The relation of the leaves, stems, and flowers has been 

 carefully worked out by Magnus and confirmed by Schu- 

 mann. The writer has nothing to add to their conclusions; 

 but in order to follow out the histological details, a brief 

 review of the facts may be useful. 



If the terminal bud is carefully dissected out, it will be 

 found that the shoot terminates in a conical tip, which pro- 

 jects considerably above the lateral organs (fig. i). The 

 leaves arise in pairs, mostly on opposite sides of the stem 

 (fig. 5). The lower one is larger, and its base extends 

 around the stem in the form of a sheath; almost as soon as 

 it is visible, there is formed, just above it, a protuberance 

 (fig. 5, ¥), which a careful examination shows to be con- 

 siderably extended laterally. Very early this outgrowth 

 shows a cleft in the middle, by which it is divided into 

 two nearly equal parts; of these, one becomes the begin- 

 ning of the branch found in the axil of the older leaf, and the 

 other the rudiment of a flower. At first it is impossible to 

 distinguish between them, but soon they undergo further 

 changes which render their recognition easy. 



If a section is made, cutting through the centre of the 

 apex, it presents the appearance shown in fig, 5. The pri- 

 mary tissue-systems are clearly recognizable and show the 

 arrangement typical of most angiospermous plants. There 

 is, as usual, a well defined epidermis, all of whose cells are 

 for some time capable of division, but the divisions are always 

 radial, and this epidermis continues without break over the 

 apex, and over the surface of the young appendicular or- 

 gans. Below the epidermis is the periblem, also composed 

 for the most part of a single layer of cells in the younger 



