54 Rennert : Seeds and Seedlings of Arisaema 



hypocotyl. This type of germination does not seem to be due to 

 a diseased condition of the seed or embryo or to an unfavorable 

 environment nor does it appear to be advantageous to the young 

 seedling. It might be suggested therefore that it is an expression 

 of an inherent tendency in aroids to carry the young plantlet as 

 far as possible in its development before an assimilatory organ is 

 produced. If this conclusion be correct we have in A. Dracontimu 

 a transition stage between a seedling forming its corm outside of 

 the seed coats with the aid of a plumule as in A. triphyllum and a 

 corm formation within the seed coats at the expense of the endo- 

 sperm as is the case with SpatJiyema foetidus. 



Explanation of Plate 3 



Fig. I. Seedling of A. Dracontium showing hypocotyl just emerging from seed. 



Fig. 2. Seedling of A. Dracoiitiuni. Hypocotyl has begun to enlarge, short root 

 has appeared. 



Fig. 3. Seedling of A. Dracontitun. Root has elongated, root hairs have arisen. 



Fig. 4. Seedling of A. Draconthtm. Hypocotyl has enlarged greatly, first root 

 has elongated, second root is just appearing. 



Fig. 5. Seedling of A. Dracontium. Hypocotyl has attained full size of first 

 year's corm. 



Fig. 6. Seedling oi A. Dracontium. Specimen in which the root system has been 

 only slightly developed. 



Fig. 7. First-year corm of A. Dracontium. Formation of periderm at base of 

 cotyledon has separated corm from seed. 



Fig. 8. Seedling of A. Dracontium which has produced plumule. 



Fig. 9. Seedling of A. Dracontium. More advanced ; note single contractile root, 

 developed only in those cases where plumule is sent up. 



Figs 10, 11, 12. Variations in form of plumule in those seedlings of A. Dra- 

 contium which send up a leaf. 



Figs. 13, 14. Second-year leaves of A. Dracontium when a plumule had been 

 developed by seedling. 



Figs. 15, 16, 17, 18, 19. First leaves produced by A. Dracontium corms which 

 have been developed without the aid of a plumule. 



Fig. 20. Seedling of .4. triphyllum. Hypocotyl just emerging. 



Fig. 21. Seedling of ^. triphyllum. Cotyledon lengthened, hypocotyl has begun 

 to enlarge, root has arisen. 



Fig. 22. Seedling of ^. /';7)^/^)'//«w- Second root appearing. 



Fig. 23. Seedling of ./. triphylhan. Second root has increased in length. 



Fig. 24. Seedling of A. triphyllum. Plumule has emerged from cotyledonary 

 sheath. 



Fig. 25. Seedling of A. triphyllum. Petiole of plumule has lengthened, a third 

 root has appeared. Hypocotyl perceptibly enlarged. 



Fig. 26. Seedling of A. triphyllum. Contractile root formed, plumule fully ex- 

 panded. 



Fig. 27. Seedling of A. hybrida. Plumule produced. 



Figs. 28, 29, 30. Variations in form of leaf [jroduced second year by .4. hybrida. 



