Anomalous Forms of Dicotyledonous Stems. 125 



Embryo-buds, first described by Dutrochet*, and considered by 

 him to be buds, which instead of becoming elongated are deve- 

 loped on all sides, and, producing no leaves, are nourished by the 

 sap of the bark. Prof. Treviranus remarks that this view is dif- 

 ficult to reconcile with the generally received opinion that the 

 formation of wood depends on the presence of leaves, and new 

 investigations upon living specimens are very desirable ; it is ob- 

 vious however that the production and development of secon- 

 dary layers of wood occurs here, quite separate and distinct from 

 the central primary ligneous body of the tree. [With regard to 

 these remarks it may be observed, that it is only if we admit the 

 notion that the new layers of wood actually grow down from the 

 leaves, like roots, as is affirmed by Gaudichaud, that there is 

 any difficulty in adopting Dutrochet's views. If the leaves only 

 elaborate the juices for the formation of new wood, the elaborated 

 sap conveyed down in the bark and cambium-layer may go to 

 form new layers around the nucleus it finds in the shape of an 

 embryo-bud, just as readily as to increase the great central woody 

 mass of the tree. — Rep.'] 



The author next notices those stems in which, in addition to 

 the central woody mass, from three to ten smaller ligneous 

 masses occur surrounding the central one and increasing in size 

 in proportion to it. Mirbel f first pointed out this structure in 

 Calycanthus floridus, and Gaudichaud \ in the Sapindacece. The 

 course of the formation of the four secondary woody masses in 

 Calycanthus is as follows : — In a young stem there are found 

 four vascular bundles in the bark, distinct from the central wood, 

 and from each other except at the nodes, at every one of which 

 cross bundles uniting these together form a ring round the cen- 

 tral body ; as the stem grows, new layers of woody substance are 

 deposited on the inner faces of these bundles (which are of 

 course carried outward with the bark to make room for the in- 

 creasing thickness of the central mass of wood). These new 

 layers are considerably thicker than the outer, previously formed ; 

 they are also progressively wider, and thus form a somewhat cres- 

 cent-shaped body (when seen in a transverse section) ; the horns 

 of the crescent advancing outward gradually approach and meet, 

 so as to include a portion of the bark, which then forms what 

 resembles a kind of pith to it. This false pith of each woody 

 mass is thus of course excentrical, the woody layers which sur- 

 round it being fewer and thinner on the outer side. 



In regard to the origin of this structure, Mirbel compared the 

 four bundles to those lying in the angles of the square stem of 



* Nouv. Mem. du Mus. d'Hist. Nat. iv. 



t Ann. des Sc. Nat. xiv. f Archiv de Bot. ii. 



