PHYSIOLOGICAL BOTANY. 205 



ration. I have several times recurred to it, and shall 

 again recur to it, because I believe that it is the key to 

 vegetable organography ; because it comprises a theory of 

 the regions (or members) (merithalles), which I defend; 

 and because it supersedes (infirme) all other theories." 

 The basis of his system is principally contained in these 

 words. 



Gaudichaud's whole theory rests upon the perfect 

 identity of the buds and the embryo, and the formation 

 of roots or root-like parts in the former as in the latter, 

 when the branch grows. This explains the increase in 

 thickness, which is always a difficulty, especially in the 

 Monocotyledons, and in the cauloma of Palms. It has 

 already been stated above, that the resemblance of the 

 embryo and the buds is not so great as Gaudichaud thinks. 

 Roots growing downwards in the stem are attributed to 

 buds from analogy only, and this is imperfect. Although 

 Mirbel explains the increase of the stem of Palms by the 

 origin of new vessels from the interior of the circum- 

 ference of the stem, yet the accurate explanation of the 

 entire process is accompanied with great difficulties, in- 

 dependently of the fact that this origin of the vessels 

 cannot be found on accurate examination. But the 

 difficulties vanish if we admit the occurrence of lateral 

 growth, which appears probable at first sight. In my 

 Lectures on Botany (Part II, Berlin, 1845, p. 309), I have 

 shown that the stem of the Date-palm in its early stage, 

 much resembles a bulb, which also at first increases in 

 thickness, and then ascends in the form of a stem ; I have, 

 moreover there (p. 237) detailed observations, which show 

 that in the stem of the Dicotyledons, a layer, sometimes 

 thick, sometimes thin, applies itself; this, however, 

 especially indicating lateral growth. Thus the roots of 

 the buds do not pass far down the stem. It is extremely 

 probable that a little cellular tissue may grow downwards 

 from the buds into the stem, but it is doubtful whether 

 vessels descend from the buds into the stem, they certainly 

 do not pass down far in this manner (see my Lectures, &c., 



