100 



than at the sides , has been formed , the nature of the cambial 

 growth undergoes a change similar to that described in the 

 case of P/iytocrene. The wood later developed is not only, as 

 already implied , of a softer , looser nature being traversed by 

 broad and very irregular medullary rays {m r) but its produc- 

 tion is very unequal, both as regards quantity and quality, at 

 different points in the cambium-ring. Thus on opposite sides 

 of the inner ellipse there is a copious production of wood 

 soon forming two broad lobes (//) while in the intermediate 

 regions at the ends of the ellipse very little tissue is given off 

 inwards by the cambium, and that is mostly of a parenchy- 

 matous character. The thought immediately suggests itself that 

 in this uneven production of wood there is a close resemblance 

 to Fliytocrene ; that the broad lobes of xylem correspond to the 

 prominences of the wood („Holzzacken") , the intermediate tis- 

 sue {s x) ^ to the areas of soft wood („Holzausfullung'') in Fhy- 

 tocrene', in fact that we have here to do merely with a sort 

 of P/iytocrene-%iQm with but two wood-prominences instead of 

 5 — 13 as in Phj tocrene itself. That this is not merely a super- 

 ficial resemblance becomes evident on further investigation of 

 the tissues in question. For the wood //in Fig. 1 shows a 

 close correspondence to the wood of the prominences in P/iy- 

 tocrene , consisting of rows of wide , pitted vessels and tracheids 

 with which rows of more or less lignified parenchyma alternate. 

 The latter, it is true, have here in a more pronounced degree 

 the character of medullary rays than in Phytocrene , where perhaps 

 they may be better regarded as wood-parenchyma of the bundles. 

 This however is a difference rather of degree than of kind. 



The parenchymatous xylem {s x) , although comparatively 

 little in quantity, bears also the closest resemblance to the 

 corresponding tissue of Phytocrene ^ both as regards shape and 

 mode of origin of its elements. The cells are developed in the 

 same way by transverse division of the cambial products into 

 spindle-shaped groups of two distinct sizes , the larger groups 

 exceeding the shorter and somewhat narrower groups two to 

 three times in length. A further resemblance of this tissue to 



