30 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



are crowded and much elongated (fig. 14) resembling those which 

 occur in a number of extinct Conifers, e. g., Xenoxylon latiporosiim 

 (Cram.) Gothan. Multiseriate pitting of the araucarian type of 

 arrangement occurs in Drimys axillaris and D. colorata, particularly 

 in the wood of the roots. Araucarian pitting also occurs in Tetra- 

 centron, in large, short tracheids that are to be found just below 

 the nodes. These tracheids (figs. 15 and 16) unlike the majority 

 of the tracheids, are abundantly pitted on their tangential as 

 well as their radial walls, and appear to function in facilitating a 

 rapid radial flow of water to the "entering" traces of the leaves 

 and rootlets. 



Particularly significant, however, is the distribution of wood- 

 parenchyma in Tetracentron, Trochodetidron, and Drimys. In the 

 first two genera and in Drimys Winteri it is diffuse. In Tetra- 

 centron and Trochodendron the parenchyma is abundant and 

 scattered throughout the thick-walled tracheids of the summer- 

 wood (figs. 7 and 13), whereas in Drimys Winteri it is usually 

 much reduced in amount. In Drimys colorata (fig. 9) and D. 

 axillaris diffuse parenchyma with transitions to terminal and 

 banded types occurs in the stem and root. 



If these facts are interpreted from the point of view of the so- 

 called laws of recapitulation, reversion, and retention, and Holden's 

 hypothesis in regard to the taxonomic and phylogenetic significance 

 of the distribution of wood-parenchyma, it is evident that Tetra- 

 centron, Trochodendron, and Drimys must be considered to be 

 primitive types of Angiosperms, since they possess diffuse paren- 

 chyma and do not show vestiges of vessels in the root, seedling, 

 node, leaf, and other supposedly conservative regions. 



There seems to be no evidence, therefore, to indicate that 

 Tetracentron, Trochodendron, and Drimys once possessed vessels 

 and have lost them. In fact, all the evidence at hand seems to 

 indicate that these genera have retained a number of ancestral 

 Gymnosperm characters. As will be shown in a subsequent 

 paper, the Magnoliaceae and allied families are extremely variable 

 in their external and internal characters, and show numerous 

 transitions from apparently primitive to advanced and highly 

 specialized tyjjes of structures. This is true of the llower, leaf, 

 node, xylem, phloem, cortex, etc. It appears, accordingly, to be 

 highly improbable that the members of this group are forms that 



