ANATOMY OF THE ROOTS OF PALMS, 431 
too, are destroyed, and the mineral matter, so often associated with the fibres, remains 
in the disorganized tissue in the form of scattered crystalline bodies. 
Some of the parenchymatous cells of the cortical tissue in front of the advancing 
root-apex possess very dense granular protoplasm and large nuclei, thus presenting the 
normal appearance of secretory cells (Pl. 48, fig. 4). The elements which intervene 
between these and the cavity surrounding the young root are very clear and refractive, 
showing signs of approaching solution. It seems highly probable that a process of 
partial auto-digestion of the cortex, no doubt in response to a stimulus received from 
the young rootlet, precedes the final solution and absorption by the poche. Should this 
prove to be the case, it will afford an interesting parallel to Prof. Reynolds Green’s 
observations on the digestion of the endosperm in certain seeds. He shows that solution 
is not entirely dependent on the direct action of the embryo, but sets in as the result of 
metabolic activity induced by the endosperm-cells themselves, 
Root-apex. 
Janczewski (14) described the root-apex of Monocotyledons as presenting a well- 
defined plerome-initial layer, a calyptrogen-layer, and an intermediate layer only one 
cell in thickness which splits behind the apex into dermatogen and periblem. 
Treub (15) finds in palm-roots a well-defined pleromic group, covered by an initial 
layer common to calyptrogen, dermatogen, and periblem. 
Cormack (11) describes the larger roots as possessing an “ enchevêtrement des trois 
initiales.” 
Gillain (12) investigated the apex of Kentia Forsteriana, and says: “dass derselbe 
dem gewöhnlichen Typus der Monocotyledonen entspricht, also drei Schichten zeigt: 
eine für Plerom, eine gemeinsame für Periblem und Dermatogen und eine für die 
Würzelhaube," being thus in agreement with Janczewski. 
In the present investigation the apices of large roots of Areca sp. and Kentia sp. 
were examined in serial microtome-sections, taken both longitudinally and transversely. 
The meristem was found to consist of a common initial group similar to that described 
by De Bary for Vanda (6) and by Janczewski (14) for the Cucurbitaeez and ` 
Papilionaceze (Pl. 48. figs. 5 & 6). The apical meristem is very bulky, and this renders 
it somewhat difficult to determine the median section. There is no doubt, however, that 
from this common apical group radiate lines of cells in all directions, the outer cells 
giving rise to the root-cap, the lateral ones to the “cortical” portion of the ground- 
parenchyma, and the axial cells to the “medulla.” 
In the ground-parenchyma certain strands of cells become slightly elongated and 
produce the procambial strands, which are thus merely local differentiations in the 
common ground-tissue (Pl. 48. fig. 5, proc.tiss.). ` 
If the root be a short one (i. e., if it has not progressed far beyond the pericyclic- 
papilla stage), the procambial tissue will be found to have the form of a series of 
independent strands (Pl. 48. figs. 7 & 8). More distally in a longer root it will present 
the form of a lobed cylinder (Pl. 48. fig. 9), and in a still longer root that of a complete 
circle (Pl. 48. fig. 10) as in the normal roots of Monocotyledons. 
