ROOT AND SHOOT. 



various organs depend especially upon their irritability, i.e. upon the manner in which 

 they react to external influences. In what follows, the organs of vegetation will be 

 characterii-ed from this point of view. 



Departing from the customary mode of view, we divide the body of the more highly 

 developed plants into two groups of organs, — Root and Shoot. In accordance with its 

 original signification, the root is that part of a 

 plant which becomes fixed on or in a substratum 

 as an organ of attachment, and in the latter case 

 serves for the absorption of nutritive matters con- 

 tained in the substratum. The shoot, or, to ex- 

 press it more generally, the system of shoots of 

 a plant, is on the other hand originally that part 

 which, becoming developed outside the substra- 

 tum, produces and increases the substance of the 

 plant, and brings forth, in addition, the reproduc- 

 tive organs, which never appear on a root. 



That both fulfil their characteristic functions 

 depends upon their different reactions to the uni- 

 versal forces of nature, gravitation, light, contact, 

 &c. That, as we shall see later, there are roots 

 which grow forth above the substratum like shoots, 

 that there are also numerous shoots which pene- 

 trate into the substratum like roots, does not alter 

 their original nature ; and only proves, as has been 

 mentioned already, that w^ith progressive develop- 

 ment of the vegetable kingdom, with progressive 

 adaptation of various organs to special require- 

 ments of life, some peculiarities may be lost, 

 whilst new ones on the other hand may arise. 

 This, however, will become clear only in the 

 further course of our investigations. 



In the first place, it will be advisable to illus- 

 trate more fully, by a few examples, the difference 

 between root and shoot. 



If we allow an Almond, for example, to ger- 

 minate in moist earth, we find after a few weeks 

 that the young plant already contained in the seed 

 becomes further developed (Fig. i): the primary 

 root {iv) has grown down into the earth, and 

 numerous thin filiform lateral rootlets {iv) spring 

 forth from it, growing obliquely or horizontally. 



Language has not waited for Botany to recognise this portion of our plant extended 

 in the substratum, as a special and peculiar organ, and to distinguish it from the 

 remaining parts by the name of Root. 



On the other hand, there rises from the germinating Almond, above the sub- 

 stratum, that part of the plant which will later on develope in the air and in the 



B 2 



Fig. I.— Seedling of the Almond (Atni%\ial:<s 

 comtnunis. iv primary root; m' secondary roots; 

 he hypocotyledonary (first) segment of the seedling 

 shoot; <- cotyledons (first leaves); st their stalks; 

 i first internode of the shoot-axis of the seedling ; 

 h its young leaves (nat. size). 



