TRIPHYLLUM AND ARISAEMA DRACONTIUM 47 
structure and the secondary roots are tetrach as arule. Some, 
however, have been observed to be triarch ; in A. triphyllum both 
primary and contractile roots are triarch. After the contraction 
of the roots the outer cortex cells are very much strained and 
twisted, but the radial elongation of the inner cells protects the 
stele from any distortion. The roots of A. Dracontium are more 
variable in all respects than those of A. triphyllum. 
The stem-bud of A. Dracontium and A. triphyllum have the 
Same structure in the resting embryo, with the exception that the 
procambium stands in the bud leaves have reached a more 
advanced stage of differentiation in A. wriphyllum. During 
the first season’s growth, however, the structure of the bud in 
the two species has an entirely different history. Like the 
roots the plumules of the A. Dracontium seedlings vary greatly 
in the state of development which they attain. As a rule the 
plumule of A. Dracontinm develops to at least a small degree 
after germination, forming a lamina and a short petiole which al- 
though it may break through the cotyledonary sheath, yet rarely 
reaches the air and is often represented only by a rudiment 2 mm. 
in length remaining permanently enclosed by the cotyledon and en- 
Wrapping in its turn the stem-bud of the next year. This undeve- 
loped plumule is cut off at the end of the season by the formation ~ 
of a periderm between it and the corm in the same way as the coty- 
lendon is separated from the corm. About 10 per cent. of the 
seedlings of A. Dracontium produce functional plumules, They 
appear at different stages during the growth of the corm, gener- 
ally when it has already attained a considerable size and in some 
cases only after the seedling has entirely separated from the seed. 
Its method of emergence from its enclosing cotyledon is exactly 
the same as that of J. triphyllum which produces a plumule nor- 
mally. As soon as the root has secured a firm hold on the soil 
and the hypocotyl is only slightly enlarged, the plumule with its 
blade recurved parallel to the petiole and rolled in at the mar- 
gin breaks through the tubular part of the enclosing cotyledon 
through a longitudinal slit which is already present in the resting 
embryo. The plumule becomes green rapidly while the petiole 
at the base of the lamina straightens out and the folded blade un- 
_ Tolls and grows larger. 
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