ROOTS OF CEETAIN PALMS. 277 



more important deviations. A cross-section of it presents to the naked eye a star 

 composed of brown lines, with obtuse, mostly bifid, rays. The microscope shows that 

 this star is formed of crowded vascular bundles. Besides these, scattered vascular 

 bundles occur singly in the centre of the star, but a central cord, like that of the other 

 palm -roots, is wanting." 



To this Hermann Karsten, who also gives a figure of the root (Die Vcget. Palm., 

 plate iii. fig. 3, and p. 63), replied that on comparing the structure described with the 

 roots of the other Monocotyledons he should not have expected to find a central strand. 



De Bary, grasping the relationship, wrote (Vergl. Anat., Engl, transl. p. 362) thus :— 



" The roots of Iriartea, finally, which are an inch in thickness, are distinguished from 

 those last described, first by the fact that their bulky vascular mass is not cylindrical, 

 but deeply furrowed, having in cross-section the form of a star with about ten blunt and 

 usually bifid rays ; further by the fact that the radial ring also is divided up into sclercn- 

 chymatous bundles, enclosing the vessels and phloem-groups, and radial bauds of paren- 

 chyma, which are sometimes narrow, 1-2 layers in thickness, sometimes many-layered, 

 and which separate the bundles from one another. Tiie middle of the star also consists 

 mainly of thin-walled parenchyma, often with lacunae, which is directly continued into 

 the radial bands of the ring, and in which bundles of sclerenchyma, each containing one 

 or more vessels and phloem-groups, lie scattered. Inside each sclerenchymatous bundle 

 the vessels are surrounded by 1-2 layers of parenchymatous cells, those of them which 

 belong to the ring standing in direct connection with the many-layered pericambium. 

 An endodermis, which is thickened here and there, appears according to Mohl's figure 

 to surround the star. Einally, in the entire parenchyma, both of the star and of the 

 cortex which surrounds it, numerous small bundles of sclerenchymatous fibres lie, each 

 enclosing in its centre 1-2 thin-walled elongated elements (perhaps sieve-tubes ?). The 

 xylem-plates in the ring appear short and irregular in cross-section ; their radial arrange- 

 ment and alternation with the phloern-plates is according to Mohl's figure often 

 indistinct, though in general to be recognized. The development of the elements, both 

 in Iriartea (Karsten) and in the roots of Pandanus, begins at the periphery of the ring, 

 and in general proceeds centripetally. According to all these phenomena, the series of 

 large roots just described are immediately connected with the type of monocotyledons 

 as special cases, in which the anatomical difiFerentiation becomes more varied, with the 

 more considerable size." 



A fourth type of transverse section of Areca-xoot may be recognized, in which the 

 xylem, phloem, and appertinent sclerenchyma do not constitute an undivided column, 

 but, on the contrary, form distinct masses having the structure and position of the outer 

 parts of a series of steles, small in diameter. Conformably with this arrangement the 

 endodermis is discontinuous, and shows as arcs of small circles (PI. XIX. figs. 3, 4, 5). 



In a fifth type, in place of some of the portions of small steles, there are entire steles 

 surrounded by a complete endodermis ; and thus, in transverse section, complete circles 

 of endodermis, corresponding with the arcs of small circles seen in the fourth type. The 

 type is, in fact, polystelic (figs. 6, 13). 



Between these five types there is continuity of transition. In fact, figs. 2, 3, 4, 5 

 are diagrams representing transverse sections taken from one somewhat tapering root. 



2r 2 



