RoscndaJil : symplocarpus axd lvsiciiiton. 151 



and Lysicliito}i point to an east Asiatic origin of both genera. The 

 much greater eastward extension in North America of Symplo- 

 carpus indicates a much earher advent of this genus in North 

 America than Lysichitoii. 



14. In all probability Sxiiiploiarpiis and Lysicliltoii trace back 

 to tropical ancestors with above ground stems. Living in a warm 

 and perhaps moist climate they grew and blossomed throughout 

 the year with very little interruption or cessation of growth. They 

 added a number of renewal shoots, perhaps 6-8, and had time 

 and material enough to complete the growth of each one. Each 

 renewal shoot bore two large foliage leaves on its main thickened 

 portion, and upon the thinner more elongated part from one to 

 three bracteal leaves, one of which was the spathe. The foliage 

 leaves w^ere all alike and separated by more or less distinct in- 

 ternodes. If the stems were erect growing the leaf arrangement 

 was probably spiral, but the divergence may have been greater 

 than 5/13. 



As the ancestors of these genera, perhaps almost identical 

 with the present ones in floral structure, migrated slowly north- 

 ward they gradually underwent changes. First came the shorten- 

 ing of the axis and the closer crowding of the leaves. As colder 

 climates were encountered it was found necessary to bury the 

 stem underground in order to live through the unfavorable season. 

 If the stems had been in the habit of branching this was given up 

 as they became very thick upright rhizomes. The foliage leaves 

 became very closely set, a few of them were reduced in size, and 

 in the one case they became modified into true scale leaves. 



The habit, however, of producing a number of renewal shoots 

 each year and terminating each one of them with an inflorescence 

 and the associated bracteal leaves was so strongly established 

 in the life history of the plants that it still persists, in spite of 

 the fact that under the rigors of a climate to which the plant was 

 not born, the largest number of these inflorescences are made 

 entirely useless and perish early. 



EXPLANATION OF PLATES. 



PLATE XXL 

 Fig. L — A group of Symplocarpus plants shortly after blossoming. A 

 number of foliage leaves are fullj^ expanded, otliers are being unfolded. The 

 middle specimen also shows the two scale leaves at the base. 



