108 ORGANOGRAPHY. 



down annually; a trunk as in trees, where it is woody and per- 

 manent; a culm as in most Grasses and Sedges, where it presents 

 a jointed appearance; and a caudex or stipe as in Tree-Ferns and 

 Palms. The term caudex is also frequently applied to any 

 woody erect or ascending root-like forms of stems, and is thus 

 sometimes nearly allied to the rhizome. (See p. 113.) 



From the nature, duration, and mode of ramification of their 

 stems, ])lants have been divided from the earliest periods into 

 three classes, called respectively. Herbs, Shrubs, and Trees. 

 Thus, all plants are called herbs Avhicli have stems that die down 

 annually to the surface of the ground; while those which form 

 permanent aerial woody stems are denominated trees or shrubs, 

 according to circumstances. Thus, the term tree is ap])lied if 

 tlie branches are permanent and arise from a trunk ; if the tree 

 is of small size, the term arbusculns is used. The collection of 

 branches which arise from the trunk and form the head of a 

 tree is called the coma, or im])ropcrly cyma by some botanists. 

 When the brandies are ijennanent and jn-oceed dii-ectly from, or 

 near to the surface of the ground, witliout any trunk, or where 

 this is very short, a shrub is formed. Tliis -when low and 

 branched very mucli at the base, is denominated a bush. The 

 term midershrub is also applied to a small shrub which is 

 intermediate in its cliaracters between an ordinary shi-ub and 

 an herb, tlms, some of its branches frequently perish annually, 

 while others are more or less i)ermanent. All the above kinds 

 of stems are connected by various intermediate links, so that in 

 many cases they are by no means well defined. 



If the terminal bud of a stem is continually developed, the 

 axis upon which it is placed is prolonged u]iwards from the 

 earth to its summit, giving oft" from its side the lateral branches, 

 as in most Firs. Such a stem has been termed an excurrent 

 stem. When the main stem is arrested in its development by 

 the process of flowering, or some other cause, and the lateral 

 buds become the more vigorously developed, so that the stem 

 appears to divide into a number of irregular branches, it is said 

 to be deliquescent. These diff*erent kinds of growth influence 

 materially the general form of trees. Tims, those witli excurrent 

 stems are usually more or less conical or pyramidal. Those 

 with delicjuescent stems are rounded or sin-cading. The general 

 aj)i)earance of trees also dejiends upon the nature of the lateral 

 branches, and ujion the angle wliich they make with the stem 

 from which they arise. Thus, if the branches are firm, and jirise 

 at an acute angle to the stem, as in the Cypress and Lombardy 

 Poplar, they are erect, and the tree is more or less narrowed ; 

 if they come oft' at a right augle, the branches are spreading or 

 patent, i\n in the Oak and Cedar ; if the angle is very obtuse, or 

 if the branches bend downwards from their origin, as in the 

 Wcei)ing Ashand Weejting Khn, they are termed weeping or pen' 



