84 THE PALM-STEM : 



ance in their original formation. A vascular bundle 

 which runs from the summit of the petiole of such a half- 

 developed leaf, through the petiole and bud, to the outer 

 surface of a part of the stem situated far lower down, 

 may, according to what has just been said, exhibit its 

 complete development and solidity at both ends, which 

 lie in organs already completed and solidified, while its 

 middle portion, in its course through the lower part of 

 the petiole and through the upper soft portion of the stem 

 (the phyllophore) concealed in the bud, is gelatinously 

 soft, and, in reference to the anatomical completion of its 

 individual elementary organs, still in a young condition. 

 In the same proportion as these soft parts advance in 

 development, as the part of the phyllophore through which 

 the vascular bundle runs becomes part of the stem, and 

 the petiole and leaf-sheath attain their full size and be- 

 come solidified, will the soft part of the vascular bundle 

 also increase in size and internal completeness, till its 

 growth is finally terminated, and it is solidified. This, 

 and nothing further, do we learn from a view of the 

 section of a bud, and when Mirbel finds in the increase 

 of solidity which the vascular bundles exhibit from above 

 downwards, a proof of the direction in which they origi- 

 nate, the validity of this conclusion must be altogether 

 contested. 



The question, in which direction the vascular bundles 

 are formed at their first origin, can only be decided by 

 direct observation of the process of their origination ; 

 therefore, only by microscopic investigation. Mirbel did 

 not neglect researches of this kind, and he states, that he 

 sometimes caught the vascular bundles at the moment 

 when they were betaking themselves into the rudimentary 

 indications of the leaves. In the examination of the ter- 

 minal buds of various Monocotyledons, especially in Iris, 

 Acorus Calamus, of the bulbs of Narcissus poeticus, I came 

 to the result, that the first indications of the vascular 

 bundles, in the form of transparent streaks, are to be 

 met with beneath the youngest leaves, in the axial portion 



