101 



that of Fhytocrene lies in the occasional occurrence in it of 

 isolated gi-oups of hard- walled elements , vessels and tracheids , 

 resembling in character the wood of the prominences. 



Upon the cause of the sudden change in the character of the 

 secondary wood after the formation of the ring r, neither the 

 anatomy nor the morphology of lodes casts any light. In Phy- 

 tocrene the similar change in the products of cambial growth 

 is intimately connected locally with development of the leaves. 

 There however the petioles undergo a considerable thickening, 

 and the strands of secondary xylem, developed in them, are 

 directly continuous with the wood of the prominences in the 

 stem, while in lodes this is not the case. In the latter plant 

 the leaves, which arise close under the vegetative point lea- 

 ving no long, naked, tendril-like end of the stem as in Phyto- 

 crene , have slender petioles, in which but little thickening 

 takes place, and the small amount of secondary wood which 

 is formed in the petioles is furthermore in no way connected 

 with the wood of the prominences , but its ducts are continuous 

 with those of the ring r. 



Passing the cambium and turning our attention to the 

 phloem , we find little to remind us of Phyiocrene. Neither is 

 there an especially great production of bast in the regions P 

 Fig. 1 opposite the areas of soft wood, where in Phyiocrene 

 the remarkable bast-plates lie, nor is the little phloem here 

 developed provided with hard- walled elements, nor finally does 

 the phloem b^ surrounding the lobes, supplied, as it is, with 

 regularly arranged sieve-tubes of great size, bear any resem- 

 blance to the similarly situated tissue (^Bastausfiillung'') in 

 Phyiocrene. The normally oriented secondary bast presents in 

 fact no anomalies whatever, being developed as groups of ele- 

 ments more or less separated by multiseriate medullary rays 

 and corresponding in general arrangement to the original bund- 

 les. It may only be remarked that, contrary to expectation 

 based on the analogy of Phyiocrene , the production of phloem 

 is more copious opposite the prominences of the wood (/5 ') than 

 between them {b-). 



