nruMios 101 



tliat the })r()i)()rti{)ii of the (rllulnr, paroiidiymatic, or fiesliy elements 

 is so mueh <]jreater than that of the woody that a woody eharaeter is not 

 apparent. In practical pharmacognosy, where dried roots are mostly 

 observed, a number of other terms for consistency, as in the case of the 

 hark, come into use. 



CLASSIFICATION OF STEMS 



Stems may he chissified as to duration, order of d('\ cloiJinciit in time, 

 position, and nature of origin, mode of extension, direction of ii;rowth 

 and nature of sup])ort, modification of form or function, and consistence. 



Duration. — As to duration, they are, like roots, Annual, Biemiial, and 

 Perennial. 



Ilrrhs. — Annual stems are those which die at the close of the season. 

 They may or may not i)ertain to annual roots. Plants possessing them 

 are called Herbs. Herbs are therefore either Annual, Biennial, or Per- 

 ennial, in accordance with the character of the root, but their stems 

 are always annual. The definition of an herb is a plant, the aerial 

 portion of which dies at the season's close. The stem of an herb is 

 denominated Herbaceous. 



Biemiial Stems. — Biennial stems are those which are jjroduced, 

 usually underground like that of the potato (Fig. 440, b), during one 

 season, and perish after the production of their branches in the following 

 season. Occasionali\", howexcr, like the cabbage, a biemiial stem is 

 aerial. 



Tubcn'. — Fleshy-thickened and biennial portions of niidcrgronnd 

 stems, such as the ])()t;ito, ai'c denominated Tubers (Fig. 410, (i). l''ig. 

 444 represents tiic undei-ground poi-tion of the ('iirciniKi, and well 

 displays the dill'erence between tubers and tubercles. 



Bulbs. — Basal biennial portions of stems which are invested by more 

 or less fleshy-thickened storage-leaves are called Bulbs. J5ulbs will be 

 classified under the subject of buds. 



Perennial Stems. — Perennial stems are those which Wvv and extend 

 their growth from year to year. They are Determinate when their 

 growth of the season is self-limited and closes with the production of a 

 sj)ecially i)repared Winter-bud, which protects the growing point for 

 continued growth tlie next season; Indeterminate, when no such bud 

 is formed, growth contimiing until the aj)ical portion is destroyed by 

 an incl(Mnent season. In the latter class we have the anomaly of a 

 ])ereiiiiial stem with an annual ti[). 

 11 



