66 Prof. Meyen's Report of the Pjogress of 



circumference of the stalk,) uniformly retained or gradually 

 diminished, and the constant order of their succession round 

 the stem, are properties which modify by their change these 

 two general cases. The greater the perpendicular distance of 

 the leaves is, the less is the slanting course of the vascular bun- 

 dle. If the proportion of the basis of the leaf to the periphery 

 of the stalk has remained, then the horizontal inclination of 

 the fibre only is uniformly and constantly impressed at the 

 very time of the displacement of the leaves. But when the 

 insertion is limited to a single arc, this inclination becomes 

 by so much the greater as that is lessened ; since the fibres 

 must deviate, some to the right, others to the left, while they 

 remain diffused with the lower courses over the whole peri- 

 phery. The shorter however the insertion is, and the smaller 

 the vertical distance, the less is the lateral divergence of the 

 leaves, which even goes so far as to imitate a whorl, and even 

 to form one. If, on the contrary, the original proportion is 

 preserved, the lateral divergence depends only on the per- 

 pendicular distance, and then the distichous arrangement often 

 remains, which is the natural one in the monocotyledons. Thus 

 it happens in the case of the double spiral lines, and the changes 

 of this peculiarity alone afford proof of the diversity of the 

 structure from the continuous stem to the articulated, from 

 the solid culm to the tubular. 



4. What part do the branches take in the structure and 

 growth of the stalk ? 



The branches that constitute the axillary inflorescence, and 

 which originated and grew at the same time with the leaves, 

 have their vascular bundles also in the same direction, and 

 contribute very little to the growth of the common stem. 

 The scanty data which science possesses respecting the rami- 

 fications of Pandanus justify the supposition that they have 

 the same origin as the inflorescence. If, however, a fresh 

 system succeeds the first, on account of the terminal inflores- 

 cence, whether it be that it proceeds from a single branch or 

 from several kinds around the same horizontal surface, it in- 

 clines itself upon the old one, and there forms all around a 

 layer, which may be compared with the annual vegetation in 

 dicotyledonous stems. 



Independent of this, branches may originate on the already 

 developed parts of the stem, in regard to which two different 

 properties may be noticed. For it may happen that the vege- 

 tation of the main axis is completed or interrupted, and the 

 productions of these branches externally belong to the fibrous 

 ligneous body of the old stem ; or that this continuous grow- 

 ing and the new productions combine and interlace with those 



