STRUCTURE OF PALM-STEMS. 131 



ra}~s run between the parenchyma of the pith and that of the 

 cortex. To this type belong most dicotyledons, Conifene, and 

 Gnetacea? (with the exception of Welwitschia x ) . 



III. Anomalous dicotyledons, differing from the last in not 

 having all their primary bundles arranged in a simple circle. 

 The extra bundles may either be in the cortex, as in some Mela- 

 stomacea? and Rhipsalideae, or they may lie in the pith either 

 scattered or arranged in rings, as in Cucurbitaceae, the herba- 

 ceous Berberidaceae, species of Papaver, Thalictrum, Amaran- 

 tus, and Phytolacca. man\- Nymphaeacese, some Begoniacese, and 

 a few species of Aralia. 



De Bary's other classes comprise anomalous monocotyledons 

 and certain higher cryptogams. 



381. To make clearer the somewhat complicated structure of 

 palm-stems which have unfortunately been selected in many text- 

 books to illustrate the histology of monocotyledons, a few general 

 statements are now given as introductory to the special treatment 

 in the note.- That portion of a palm-stem which lies above the 

 lowest active leaves (better called fronds) is of a conical shape, 

 is often much elongated, and carries all the new and forming 



1 For a description of this interesting plant, and an account of its peculiari- 

 ties of structure, consult J. D. Hooker on Welwitschia. 



2 The exposition by de Bary of the structure of the simpler forms of Palms is 

 given nearly in full in the translation which follows : - 



" Since the appearance of Mohl's Palinenanatomie, the following main char- 

 acters have been recognized as belonging to the simple palm-type. 



"All the bundles in the cylinder (with some doubtful and certainly extremely 

 insignificant exceptions which will be mentioned later) are leaf-traces. The 

 base of the leaf includes the whole circumference of the stem, or at any rate 

 the greater part of it. The leaf-trace is always several threaded : generally it 

 consists of many threads, in stout stems even of a couple of hundred ; its width 

 is nearly the whole of the circumference of the stalk. From the base of the leaf 

 the threads curve down into the cylinder, within which they descend, some in 

 its outer surface and nearly radial and perpendicular, others radial and oblique, 

 first pressing inward toward the long axis of the cylinder in a curve which is 

 convex towards the upper and inner side of the stem, then curving outward, 

 and gradually passing towards the outer surface of the cylinder, and in propor- 

 tion as they approach this, approximating towards a perpendicular position. 

 All threads descend through many internodes, and unite at last in the outer 

 portions of the cylinder with others which enter it further down, attaching 

 themselves to these in a direction which is sometimes tangential, sometimes 

 radial, and sometimes oblique. Until this attachment of their lower ends, the 

 bundles run independently. The union of the lower ends of bundles with 

 others that enter the cylinder lower down generally takes place in such a way 

 that the whole number of the bundles in successive internodes of equal cir- 

 cumference remains about the same. As the successive internodes and leaves 



