166 ■ COMPENDIUM OF GENERAL BOTANY. 



below the apex of the stem ; the internodes are therefore very 

 short, later many of them become much elongated. In general, 

 it is found that the basal nodes remain shoi-t, followed by long 

 nodes in the leaf-bearing region and again by short nodes near the 

 apex; the phyllomes are correspondingly crowded near the base 

 (basal rosette of many plants), higher up they are farther apart, 

 then again more crowded near the apex. In the caulome of *' un- 

 limited " growth longer and shorter internodes frequently alter- 

 nate ; in such cases we lind that the eataphyUarij leaves are crowded ; 

 they indicate the boundary between two annual gi'owths. Upon 

 these follow foliage-leaves on elongated nodes, then again cata- 

 phyllary leaves on shortened nodes, etc. 



Vertical shoots are, as a rule, structurally alike on all sides ; hori- 

 zontal branches and twigs, especially such as rest on the soil, show 

 considerable difference of structure between the upper and lower 

 sides. For example, it is found that the leaves on the horizontal 

 stems of conifers occur along the sides to the right and left; in some 

 mosses and in Selayinella there are structurally different upper and 

 loioer leaves. Upright shoots, therefore, have a I'adial structure, 

 while horizontal organs have a dorsiventral structure (Sachs). 

 These structural differences, which are dependent upon the in- 

 fluence of gravity and sunlight, also modify the haVnt of plants. The 

 study of the stem and branches of the pine will make clear what 

 has just been stated. 



The bud is either terminal or lateral ; in the latter case either 

 axillarij, or adventitious when its position is at indefinite points 

 along the stem and not in the axil. 



Vernation is the term applied to the position of leaves in the 

 bud. The relative position of several leaves in the bud is called 

 cesti'oation. Both conditions, compared with the mature state of 

 the organs, show their peculiarities. 



In regard to vernation the simplest case is where the leaf lies 

 flat in the bud ; the individual leaf may, however, be bent, folded, 

 or rolled, either longitudinally or transversely. 



Estivation, is valvule when the margins of the leaf-organs touch 

 each other, or imhricate when the margins overlap; this latter may 

 again be spiral or cpiiucuncial (flve-ranked), etc. 



Before passing to the second chapter of this section we shall 

 introduce a few statements in regard to nietamorphosis and correla- 

 tion. 



