2lt VEGETABLE ORGANOGRAPHY. 



analogy with that which takes place in the branches of 

 stems, appears to me for the present very reasonable ; 

 but I confess that sufficient proofs to clear up the point 

 are wanting. Is it developed at a fixed period ? Does it 

 fall off, or is it destroyed within a given time ? Is it 

 capable of being changed into radical branches ? What 

 is its mode of growth in length and thickness ? All 

 these questions still require to be studied by direct 

 observation. 



Roots, considered as to their general form, present 

 themselves under two very distinct appearances : the 

 one kind, which I shall call with a single base (a base 

 unique), have a conical trunk, simple or branched, but 

 single at its base ; and at the period of their first deve- 

 lopment their radicle, which is already entirely developed, 

 only elongates or ramifies. These compose a great pro- 

 portion of the roots which Richard has designated by 

 the term Exorhiz^, and which exist in the greater 

 number of Exogens, The others, which I shall call 

 FASCICULATED, proceed in bundles, more or less distinct, 

 from a common base, which is confounded with the neck 

 of the plant, and may sometimes be taken for the base 

 of the stem, and sometimes for the principal trunk of 

 the root. These come exactly within the class of Ex- 

 DORHiz^ of Richard ; they are found in the greatest 

 number of Endogens, and in Exogens with fasciculated 

 roots. The chevelu can exist in both classes of roots, 

 but is much more frequent in the first. Let us pass 

 rapidly in review the diversities of form in these two 

 classes. 



Among the roots which have a single origin, the prin- 

 cipal differences can be derived from the degree of their 

 ramifications ; some are much branched, and usually 

 abundantly provided with chevelus ; they are called 

 Fibrous Roots ; others, less frequent, are nearly 



