70 MORPHOLOGY OF STEMS. 



the whole section, or when few in number of somewhat definite 

 position or arrangement. The ordinaiy appearance of such a 

 stem, both on the longitudinal and the cross-section, is shown 

 in Fig. 126 ; it may also be examined in the Cane or Rattan, 

 the Bamboo, and in the annual stalk of Indian Corn or of 

 Asparagus. The appearance of ordinary wood is very familiar. 



135. The newer woody bundles of an endogenous stem are vari- 

 ously intermingled with the old. When, DeCandolle gave the name, 

 it was supposed, from Desfontaines's researches, that the older 

 bundles occupied, or came at length to occupy, the circumference 

 of the trunk, while only new ones were formed in the centre ; 

 and that increase in diameter, when it took place at all, resulted 

 from the gradual growth and distention of the whole. Hence 

 the contrasting name of endogenous, or inside growing, and for 

 such plants the name of ENDOGENOUS PLANTS, or ENDOGENS. 

 Our actual knowledge of the structure and growth of these stems, 

 as will be seen, cannot be harmonized with this view in any 

 way which gives to the name endogenous an appropriate signifi- 

 cation. The name continues as a counterpart to the more correct 

 one of exogenous, and as a survival of former ideas. 



136. The Endogenous Structure (so called) of the stem is cor- 

 related with a monoeotyledonous embiyo (39), usually with a 

 ternary arrangement in the flower (322), and commonly with 

 parallel- veined leaves. (173.) Endogens, although they have 

 many herbaceous and a few somewhat woody representatives 

 in cool temperate climes, mostly attain their full variety of fea- 

 tures and rise to noble arborescent forms under a tropical 

 sun. Yet Palms the arboreous type of the class do extend 

 as far north in this country as the coast of North Carolina (the 

 natural limit of the Palmetto, Fig. 126) ; while in Europe the 

 Date and the Chamasrops thrive in the warmest parts of the Euro- 

 pean shore of the Mediterranean. The* manner of their growth 

 gives them a striking appearance ; their trunks being unbranched 

 cylindrical columns, rising to the height of from thirty to one 

 hundred and fifty feet, and crowned at the summit with a simple 

 cluster of peculiar foliage. Palms generally grow from the 

 terminal bud alone, and perish if this bud be destroyed ; the}' 

 grow slowly, and bear their foliage in a cluster at the summit of 

 the trunk, which consequently forms a simple cylindrical column. 

 But in some instances two or more buds develop, and the stem 

 branches, rarely and accidentally in ordinary species, regularly 

 in the Doum Palm of Upper Egypt, and in the Pandanus, or 

 Screw-Pine (Fig. 69), which belongs to a family allied to Palms : 

 in such cases the branches are cylindrical. But when lateral 



