242 Dr. Schleiden on the Anatomico-physiological 



appearance), but a peculiar arrangement of the vascular 

 system which may always be demonstrated by anatomy. For 

 there is formed from two or more vascular bundles by sim- 

 ple superposition on one another, or by anastomotic ramifica- 

 tions, a loop, ansa, and only from this plexus do the peripheri- 

 cal organs receive their vascular bundles. From this relation, 

 then, in connexion with the formation of the horizontal me- 

 dullary rays, results infinite variety in the woody body. This 

 ansa is, at the same time, especially destined to place the 

 parenchyma of the lateral organs in connexion with the pith 

 (or, rather, the living parenchyma) of the axis. The size of 

 the noose is therefore essentially dependent on the thickness 

 of the base of the leaves or lateral buds, (or, rather, the re- 

 verse). 



In the Monocotyledons this formation of true nodes is 

 probably far more rare, if indeed it occurs at all; for I am yet in 

 doubt whether a real anastomosis of the vascular system takes 

 place in the so-called nodes of the grasses, for the purpose of 

 giving off bundles to the lateral parts. Thus much at least 

 is certain, that in Monocotyledons the anastomosis of the 

 vascular system decidedly takes place more rarely than in 

 Dicotyledons. If it could be ascertained that the above cha- 

 racteristic formation of nodes nowhere occurred amongst the 

 Monocotyledons, this would certainly afford a primary and 

 general distinction between them. 



In Acotyledons the decided dicotyledonous formation again 

 occurs ; and many unnecessary words would have been spared 

 on the pretended difference in the stems of Ferns if the forma- 

 tion from which it is said to deviate (viz. the dicotyledo- 

 nous stem) had been studied, not in a limited consideration 

 of the Oak or the Lime, but in the various types of the differ- 

 ent families. I believe it would not be very difficult for me 

 to demonstrate all the modifications of the woody tissue of 

 ferns, which do not depend on the closing up of the vascular 

 bundles, but only on number, situation and mutual combina- 

 tion, as occurring in all essential points in the EuphorbiacecB 

 or the Cactece, 



B. In every case where vascular bundles go off to a peri- 

 pherical organ, they must decussate with the subsequently 



