97 



abundant xylem of a comparatively hard and firm nature is 

 given off, while the intermediate portions of the cambium pro- 

 duce in general only parenchymatous elements of smaller size. 

 The firm wood of the prominences („Zackenholz") consists of 

 remarkably wide , pitted ducts , tracheids, and wood-parenchyma. 

 The soft wood of the intermediate areas („Holzausfullung") is 

 made up of spindle-shaped groups of cells , each group being 

 the product of a single cambial cell-division. These groups are 

 of two distinct forms or rather sizes ; the larger consist of 

 5 — 9 cells and are always considerably longer than the smaller, 

 which contain but 1 — 3 slightly narrower cells. Outward from 

 the wood-prominences the cambium gives off a phloem which 

 is, in its greater part, destitute of hard elements and resem- 

 bles more or less the soft xylem just described , but contains 

 frequent, irregularly distributed groups of small sieve-tubes. 

 Outward from the areas of soft xylem , however, the phloem is 

 richly provided with hard elements , and of a very firm texture. 

 These portions of the phloem, long known as „bast-plates", 

 are also rich in sieve-tubes of large size. While the wood- 

 prominences, through the repeated radial division of the cells 

 in the surrounding portions of the cambium, come soon to 

 assume a somewhat triangular form , the areas of soft wood 

 as well as the bast-plates do not increase in breadth during 

 the progress of secondary thickening, but retain an approxi- 

 mately rectangular form. The number of the alternating wood- 

 prominences and bast-plates stands in close relation to the leaf- 

 arrangement (in Phytocrene spiral, "^k — ^/is), and in such a 

 way that the bast-plates correspond in the main to the orthos- 

 tichies. The origin and development of the renewed cambium- 

 rings in the cortex, as well as the peculiarities in the forma- 

 tion of the periderm may here be neglected , as none of the 

 plants to be described show, so for as the author's observations 

 reach, similar phenomena. 



After this review of the more important anatomical charac- 

 ters of the P//2/iocrene-S'peciGs , which have already been inves- 

 tigated, we may proceed at once to the consideration of 



