468 On the Structure of Roots. 



a manner suitable for the instruction of those who do not possess 

 strict scientific knowledge. 



In dealing with plants we have great advantages over those 

 who devote themselves to the higher branch of the organic crea- 

 tion, in the simplicity and obviousness of the parts of the struc- 

 ture, and the functions these fulfil. When the botanist distributes 

 the various portions of a flowering-plant under the heads oi organs 

 of vegetation and organs of reproduction — and subdivides the former 

 into root., stem, and leaf, and the latter into envelopes, essential 

 organs, fruits, and seeds — his operation is merely the carrying out 

 more strictly and accurately of an arrangement of objects familiar 

 to everyone, into classes which are more or less clearly and fully 

 comprehended by all those who have thought or talked about 

 plants. The three great classes of agricultural produce, seeds, 

 roots, and fodder, already correspond to the most important of the 

 above heads, and the well-known differences in the modes of treat- 

 ment requisite to cause predominance of any one or other of these 

 classes of products in any given plant, indicate the importance of 

 studying the parts or organs separately as well as collectively. 

 Yet tlie well-being of a plant, in a state of nature, depends upon 

 the balance maintained between tlie tendencies of its different 

 parts ; tliese tendencies being in some particulars quite opposed 

 to each other. External conditions may greatly disturb the 

 balance, so that one tendency manifests itself in excess, in which 

 case it is ordinarily at the expense of another tendency. This is 

 strongly shown in the oppositi(m between the tendencies residing 

 respectively in the two classes of organs which are denominated 

 vegetative and reproductive. When a })lant produces the first class 

 of organs in unusual luxuriance, tlie production of the second 

 class is impeded ; and vice versa, when plants are starved in their 

 vegetation the whole energy appears to throw itself into the 

 reproductive system, to save the race, as it were, even if the in- 

 dividual must perish.* Illustrations of these general reflections 

 will suggest themselves to every thinking cultivator, and it is 

 needless to dwell at length upon them. They are thrown out here 

 by way of explanation of the present inquiry, in which we shall 

 endeavour to elucidate the most important points of the natural 

 history of one kind of organ, the Root, of the plants chiefly cul- 

 tivated by our farmers, or forming troublesome weeds, but in which 

 we shall be compelled also to undertake the examination of roots 

 generally, and to treat the root not as an independent product, but 

 as an essential part of the structure of the higher classes of plants. 



* For instance, we have seen the common garden poppy growing in a neglected 



mignonette-box, with fully -developed flowers, where the entire little plants were 

 little more than an inch high. Such examples are common on barren soils. 



