374 BOTANICAL GAZETTE [april 



are employed which are alkaline in nature and have the objection of staining 

 the background. — Ernest F. Artschwager. 



Size variation in secondary xylem. — Bailey and Tupper^ have applied 

 the comparative method in thoroughgoing fashion to an attack on the problem 

 of cell size. Confining themselves to a study of the length of the tracheary 

 elements in the secondary xylem of trees and shrubs among vascular cryp- 

 togams, gymnosperms, and angiosperms, they present data derived from 

 thousands of measurements on some 440 species belonging to 124 famihes. 

 The most conspicuous fact brought out by this reconnaissance survey is that 

 the length of these elements is roughly correlated with phylogenetic position, 

 being greatest in vascular cryptogams, somewhat less in gymnosperms, and 

 least in angiosperms. This progressive reduction in the length of the wood 

 cells has been associated with the reduction in amount of the primary xylem 

 in the passage from lower to higher forms, but is probably due in greatest 

 measure to the evolution and differentiation of vessels. These elements have 

 become progressively shorter and broader, thus losing their resemblance to the 

 primitive tracheid; and the fibers and tracheids associated with them have also 

 grown shorter, although naturally to a less extent. Notable exceptions to the 

 general rule are the vessel-less Magnoliaceae and Trochodendraceae, represented 

 by Drimys and Trochodendron, which possess tracheary elements far longer 

 than other angiosperms, and thus resemble the gymnosperms. Evidence from 

 this source obviously supports the view that these genera are primitive rather 

 than reduced types. 



The authors have also made a preliminary study of the relations between 

 the length of the tracheary elements and the age of the plant, its growth habit, 

 and the environment under which it lives. So far as the cells studied are 

 concerned, there is no definite correlation between body size and cell size. The 

 tracheary elements may increase in length for a few years as the plant grows 

 larger, but they soon reach a constant size. Dwarfed and depauperate plants 

 tend to have somewhat smaller elements than normal individuals. 



The authors point to the need of more intensive investigations in this 

 hitherto almost unexplored field; and in particular call for a careful study of 

 the activities of the cambium and the factors which direct these activities. 

 Indeed the growing point of plants, once so enthusiastically studied as the key 

 to histology and then for so long neglected, bids fair to be once more a center of 

 interest as one of the keys to a knowledge of morphogenesis. — E. W. Sinnott. 



Sap concentration in epiphytes. — Continuing the studies already noted' 

 upon the concentration of tissue fluids, Harris^" has found in several species of 



* Bailey, I. W., and Tupper, W. W., Size variation in tracheary cells. I. A 

 comparison between the secondary xylems of vascular cryptogams, gymnosperms, and 

 angiosperms. Proc. Amer. Acad. 54:149-204. ^g^. 6. 1918. 



9 BoT. Gaz. 65:285-286. 1918. 



'» Harris, J. Arthur, On the osmotic concentration of the tissue fluids of desert 

 Loranthaceae. Mem. Torr. Bot. Club 17:307-315. 1918. 



