428 DR. ERIC DRABBLE ON THE 
Mangin, 1882 (9), in a very important paper entitled “Origine et Insertion des 
Racines adventives . . . chez les Monocotyledones,’ gives an accurate account of the 
connection of the bundles of adventitious roots with those of the stem. He shows that 
the young root first appears as a papilla formed by local hypertrophy of the pericycle ; 
in this young root the vascular elements arise and differentiate both internally, 
i.e., in the ground-tissue of the central cylinder of the stem, acquiring connection 
with the scattered stem-bundles, often penetrating very deeply into the stem, and also 
externally into the developing root-apex, keeping pace with the growth in length of 
the young root, in which the bundles are arranged in a circle embedded in a 
fibrous or sclerenchymatous zone generally conforming to the typical root-structure of 
Monocotyledons. 
Drude, 1887 (10), in his article on the Palmacez in Engler and Prantl’s * Natürlichen 
Pflanzenfamilien, gives a short account of the buttress-roots and contractile roots of 
some palms. 
Cormack, 1896 (11), made a great step in advance when he discovered what he 
termed a “ polystelic ” condition in the roots of Areca, and the common occurrence of 
a lobed and interrupted cylinder in many palm-roots. He grouped the arrangements 
met with under several headings, commencing with the normal type possessing a 
complete endodermis surrounding a central fibrous or sclerenchymatous ring in which 
lie the xylem and phloem elements. Passing through the condition in which the 
cylinder is still complete, but longitudinally lobed, the endodermis dipping into the 
depressions but being quite continuous, he came to those roots in which the central 
cylinder is composed of a series of independently running strands of fibrous tissue 
presenting the form of arcs of circles in transverse section; between these the 
endodermis dips in and becomes discontinuous; and finally he described the case of 
Areca, where one or more of these independent strands presents a complete radially 
symmetrical cylinder or “stele,” as he terms it, round which the endodermis is 
complete. Cormack further shows that some roots exhibit the more complicated of 
these conditions in the proximal regions and the simpler types in the distal, and dis- 
cusses the question as to whether this is due to secondary changes in the proximal 
regions brought about by dilatation-parenchyma, or other agency, acting subsequently to 
the apical development, or whether it is due to progressive simplification of the apical 
mersitem. He inclines to the latter view, supporting his contention by an ingenious 
deduction from the number of protoxylem-groups. He finds that the number of these 
is less in the distal and apieal regions than in the proximal, and points out that pro- 
duction of a greater number of protoxylem-groups by secondary changes is extremely 
improbable if not impossible, and hence concludes that we are here dealing with a 
. gradual reduction and simplification as apical development proceeds. 
Cormack attempts an explanation of the peculiarities of structure met with in palm- 
roots based on physiological considerations of mechanical support, but does not attempt 
a morphological explanation. 
Gillain, 1900 (12), deseribes the structure of the roots in a larze number of Palms, 
but, curiously enough, he finds none with lobed or divided cylinders. He notices that 
