ANATOMY OF THE ROOTS OF PALMS. 415 
In Ptychosperma filifera (Pl. 50. fig. 65) the metaxylem forms tangentially extensive 
groups, from the peripheral surface of which extend as many as three protoxylem-groups. 
In this way a ring of xylem is formed in the periphery of the cylinder, with numerous 
but narrow interruptions. 
In Cyrtostachys Renda (Pl. 50. fig. 62) a highly interesting condition is found in the 
presence of two or more xylem-groups, with inverted orientation, accompanied by phloem, 
the protoxylem being placed towards the centre of the root, lying in the internal portion 
of the fibrous ring. These xylem-groups are accompanied laterally by one or two 
phloem-groups. 
A similar but less pronounced feature is seen in Zcuala gracilis (Pl. 50. fig. 64). 
Here, however, the inverted xylem is not accompanied by phloem. 
In Latania Commersonii (Pl. 50. fig. 72) the internal boundary of the fibrous zone 
abutting on the pith is irregularly lobed and in some of the lobes lies one of the large 
internal vessels. 
In Phenix dactylifera (Pl. 50. fig. 68) two lobes of the fibrous zone, each enclosing a 
vessel, project deeply into the pith. 
In Sabal glaucescens (Pl. 50. fig. 67) a band of fibrous tissue extends completely 
across the pith and in this lie two vessels. 
In Livistona australis (Pl. 50. fig. 66) a fibrous strand completely separated from the 
fibrous zone of the cylinder traverses the pith and contains a single vessel, while a 
similar strand in Ptyehospermum filifera (Pl. 50. fig. 65) encloses two vessels. 
In Licuala gracilis (Pl. 50. fig. 64) there are three medullary strands, two of which 
contain a number of vessels, the larger occupying the centre and the smaller ones 
radiating from these in a manner generally resembling the arrangement of vessels in a 
small pithless root—7. e., an exarch radial arrangement of xylem. 
In Areca sp. (Pl. 50. figs. 55 & 76) the presence of phloem-groups in the medullary 
strands alternating with the radial xylem-groups heightens the resemblance to a root- 
cylinder. 
As the medullary strands are followed down the roots the number of vessels contained 
may decrease, but the strands remain as separate structures for a very longdistance. In 
Livistona australis one was followed for 12:1 ems. without showing any sign of fusion 
with the fibrous zone. 
J UNCTION or BUNDLES OF ROOT AND STEM AND ESTABLISHMENT OF 
NorMAt Root-cYLINDER. 
Mangin (9), in 1882, found that two distinct methods of junction of the bundles of 
adventitious roots with those of the stem occur in Monocotyledons. In the majority of 
forms the bundles of the root join on to a few of the outer bundles of the stem, or, in 
the case of large roots, on to a considerable number of peripheral stem-bundles. In the 
Palmaces and Pandanaces, however, connection is established not only with the 
peripheral stem-bundles, but also with others more deeply placed, the connecting strands | 
being differentiated in situ in the ground-parenchyma of the stem. | 
SECOND SERIES.— BOTANY, VOL. VI. 38 
