138 COMPOUND ORGANS OF PLANTS. 



ments, heat can be detected in any ordinary cluster of flowers. 

 The best plants for experiment are the Aracese, where the heat 

 is confined and reveberated by the hood-like inflorescence. In 

 some of these plants the temperature rises at times to 20° and 

 50° Fahrenheit, above that of the surrounding air. The tem- 

 perature rises from the first opening of the flowers, and reaches 

 its maximum when they shed their pollen, at which time the 

 heat developed is so 'great as to be perceived by the hand j it 

 afterwards gradually declines until the flowers fade. 



CHAPTER XI. 



THE ESSENTIAL REPRODUCTIVE OROANS. 



THE ANDRCEOIUM OR STAMINAL ORGANS. 



The stamens are situated immediately within the corolla, and 

 form the third verticil of the flower. They constitute, collec- 

 tively, the androecium (iM'9jp a male, and amiov habitation), or 

 the male sexual organs of the plant. 



There is a power given to all plants of developing new plants 

 out of any of their cells, when these cells are placed in suitable 

 circumstances. In the cells of plants in general the expression 

 of this law seldom occurs, since it is only in rare cases that the 

 necessary conjunction of all the conditions is brought about. 

 Nevertheless, there are cases in which the ordinary leaves of 

 the stem may be made to develope new plants, as, for instance, 

 the leaves of Bryophyllum calycinum which, when placed on 

 moist earth, develope young plants from the indentations of their 



