f 



1 12 ORGANOGRAPHY. 



surface one or more buds, as in the Crocus {figs. 219, a, b, and 

 220), where they proceed from the apex, and ultimately destroy 

 their parent by feeding upon its accumulated 

 Fig. 221. nutriment. These new corms, in a future 

 year, also produce others near their apex, 

 which by developing at the expense of their 

 parents destroy them in like manner, and 

 these again form other corms by which they 

 are themselves destroyed. In this manner 

 the new" corms, as they are successively deve- 

 loped come gradually nearer and nearer to 

 the surface of the earth. In the Colchicum 

 {fig. 221), the new corm a'", is developed on 

 one side of the old corm, near its base. This 

 feeds upon its paient, and ultimately destroys 

 it, and is in like manner destroyed the next 

 year by its own progeny. Thus, in taking up 

 such a corm carefully, we find {fig. 221), a, 

 Fig. 221. Colchicum. the shrivelled corm of last year ; and a", that 

 a.^shrfveiied^^re- of the present season, which, if cut vertically, 

 mains of last year's shows a"', the corm in a young condition 

 corm. a". Corm of p , , ' , .-,■, *' i. • i. u 



the present year. lor the next year. Ail corms contain starch 

 a'".commencement or other nutritious matters, which are stored 

 of the corm of next r ^\. n ^ r i.u • xs? 



year. up for the future use of their offspring. 



Section 2. The Eoot or Descending Axis. 



The root is defined as that part of the axis which at its 

 first development in the embryo takes an opposite direction to 

 the stem (hence it is termed the descending axis), avoiding the 

 light and air, and fixing the plant to the soil or to the substance 

 upon which it grows, or floating in the water when the plant 

 swims upon the surface of that medium. The part where the 

 stem and root diverge is called the neck {fig. 227, c). The axis 

 is here generally more or less contracted, at least in the young 

 plant ; but, as development proceeds all traces externally of this 

 point are usually destroyed, so that after a few years it becomes 

 very difficult, if not impossible, to discover its position. That 

 part of the root which joins the stem is called the base, and 

 the opposite extremity the apex. 



We distinguish two varieties of roots, namely, the True or 

 Primary, and the Adventitious or Secondary. 



1. True or Primary Root. — The true root, which can only 

 exist in Dicotyledonous plants (see page 120), is formed at first 

 by additions made within the extremity of the radicle of the 

 embryo ; and the mode in which it takes place may be thus 

 stated : — GroM'th commences by the multiplication of cells by 

 division, just within the apex of the radicle {fig. 222, a) ; these 



