144 MINNESOTA BOTANICAL STUDIES. 



behavior is similar to Syiii[^locaypiis. However, as the total num- 

 ber of leaves produced each season is greater in Lysichifon than 

 in Syuiplocarpns, the number of inflorescences laid down each 

 year is also larger than in that genus. Whether this is due to 

 the longer growing season which obtains in the region where 

 Lysichiton is native or to an ancestral habit cannot be definitely 

 stated. Five to seven renewal sh.oots, and consequently as many 

 inflorescences, are not uncommon on vigorous plants (Text-Fig. 4). 

 More of these mature each season than in Symplocarpus. Most 

 of the plants have two to four and even five flower stalks (Plate 

 XXI, Fig. 2). It is very likely that sometimes all the inflorescences 

 which are laid down mature, especially on plants producing only four 

 or five renewal shoots each year, for not infrequently one finds 

 on such plants remains of last year's flowering stalks among 

 the decaying bases of the last normal foliage leaves of the same 

 season. On the larger plants blasted inflorescences are frequently 

 found among the bases of the foliage leaves. They do not, 

 however, seem to be as reguarly confined to the latter part 

 of the season's growth as in Symplocarpus. 



The difference in the behavior of these two northern aroids 

 in regard to the maturation of the inflorescences and in the special- 

 ization of some of the leaves is perhaps largely to be accounted 

 for, as has already been stated, by the climatic conditions under 

 which they live. In the case of Symplocarpus a long cold winter 

 season has to be endured, during which time all life activities com- 

 pletely cease. The spring transition period and time for blos- 

 soming is short, so that the summer season and time for active 

 vegetative growth soon follow. The seasons are extreme and 

 the transition between them rapid, and as a result a very pro- 

 nounced rhythm has been established in the life of the plant. The 

 period favorable for blossoming has become so short that most 

 of the inflorescences made for each year never reach maturity. 

 The modification of several foliage leaves into highly specialized 

 colored scale leaves are adaptations made to reconcile the early 

 blossoming habit with the cold spring that is encountered. 



In the case of Lysichiton no such seasonal extremes are ex- 

 perienced. The milder winter season passes gradually into a 

 much earlier spring, spring is more prolonged and grades into 

 a moderate summer. The result is that fewer inflorescences be- 



