52 RENNERT: SEEDS AND SEEDLINGS OF ARISAEMA 
sion of a plumule, of course, prevents the destruction of young 
seedlings by grazing animals; but the well-developed plumule 
contains enough raphide cells to protect it from attacks of this 
kind and the advantage which the plants enjoy in this respect 1s 
largely over-balanced by positive disadvantages. This variation, 
oe er 
siete aes 
therefore, can scarcely have been perpetuated because of the ad- _ 
vantage as a means of defense which plumuleless seedlings pos- 
sess. As far as can be discovered at present this variation is of — 
no benefit to the plant but, on the contrary, there are great disad- 
vantages in this method of germination, which tend to throw the 
plant entirely upon the food supply of the parent form for another — 
season, 
The germination of A. Dracontium consists essentiallf in the — 
conversion of the hypocotyl of the embryo into the corm of the 
seedling by the transfer of the food material contained in the — 
endosperm. In some aroids,* this resorption of the endosperm — 
and conversion of the base of the hypocotyl into a corm takes — 
place before the embryo leaves the seed; that is to say, the deaat 
velopment of the seed is not completed until a bulbiform embry? 
with true fibro-vascular bundles and no trace of cotyledon has been 
formed. An example of this type is Spathyema foetida. When uy 
the seed of this plant germinates the stem-bud pushes out of the 7 
micropyle and breaks through the ground first ; later adventitious — 
roots spring from the nodes. 
this seed and the sprouting of the first year’s corm of A. Dracot 
tium is the fact that in the former case the seed coats which suf 
round the bulbiform embryo must be penetrated by the stem-bud. 
If the corm formation of the seedling of A. Dracontium took — 
place within the seed coats (and this could be brought about — 
simply by the arrest of the elongation of the cotyledon) the tw? ‘i 
cases would be exactly similar. In fact the cotyledon of Ae 
Dracontium is varying in just this direction, for it often displays 4 q 
tendency to be shorter than the cotyledon of A. ¢riphyllum ® a 
has been pointed out above. The delay in germination at first © 
moreover, may be another indication of a tendency to carry Oe 
the entire development of the corm within the seed. 
_- ae 
* Engler. Monographiae Phanerogamarum, Araceae, 11: 34. : 
No primary root is produced. Tt — 
will be seen that the only difference between the germination of 
