404 Scott & Sargant . — On the Development of 
energy in the yearly production of contractile roots for burying 
purposes. The result is that the vegetatively produced plant 
flowers much younger than that produced from seed, which 
rarely flowers before the seventh year. 
Internal Morphology. 
Any account of the curious second-year seedlings of Arum 
maculatum would be incomplete without some examination 
of their anatomy. Certain points in their external mor- 
phology must otherwise remain obscure. External characters, 
for instance, are insufficient to determine either the homology 
of the tuber, or the way in which the cotyledon is detached 
from it at the proper age (cf. Figs. 4 and 5). Irmisch 1 , in 
describing the mature plant, has rightly stated that its tuber 
represents the stem-axis of the previous year. This cannot, 
however, be true of a seedling which has just germinated. 
The tuber of that drawn in Fig. 2 clearly forms part of the 
main axis, but we cannot tell from inspection whether the 
stem alone has been enlarged or part of the root as well. 
And in that part of the tuber which represents the stem there 
is no external mark to divide the plumule from the hypocotyl. 
These questions will of course be settled when the course 
of the bundles in the tuber has been worked out, but we may 
so far anticipate our results as to say that the tuber does 
not show complete root-structure until we reach its base, 
and it may therefore be considered as belonging entirely 
to the stem. Moreover, the greater part of it represents the 
axis of the plumule, for the cotyledonary traces do not 
bend inwards to join the central cylinder for some distance 
below the insertion of the cotyledon. 
The raphides which give the juice of Arum its acrid quality 2 
are abundant in cotyledon, stem-leaves, and in the periphery 
of the tuber. The cells which contain them are larger than the 
1 Irmisch, Zur Morphologic der monokot. Knollen- und Zwiebelgewachse, 
Berlin, 1850, p. 164. 
2 Stahl, Pflanzen und Schnecken, Jena, 1888, p. 85. 
