136 



HUTCHINSON'S POPULAR BOTANY 



flowers there is a distinct rise of temperature at the period of open- 

 ing, a fact the truth of which may be demonstrated by a thermometer 

 in the case of inverted tubular and bell-shaped flowers, the air in. which 

 is not only warmed, but, being little disturbed by the surrounding atmo- 

 sphere, retains its warmth. Kerner (Natural History of Plants) has recorded 

 the results of some experiments in this direction which are very interesting. 

 The temperature inside the spathe of one of the Brazilian Aroids, the hand- 

 some large-leaved Monstera deliciosa, was found to be 38 centigrade, when 

 the temperature of the outer air was only 25 ; the spathe of another Aroid, 



4 '/ 



Si ', * 



[E. Step. 



FIG. 172. SWAN'S-NECK THREAD-MOSS (Mnium hornum). 



One of the most beautiful of our mosses, forming deep and extensive carpets of golden green, above which nod the 

 spore-capsules on their arched thread-like stalks. It may be found on sandy woodland banks, fruiting in the spring. 



Arum cordifolium, was 35-39 at the same air temperature ; while Arum. 

 italicum, a plant extremely common in the region of the Mediterranean, 

 closely resembling our common Cuckoo-pint, actually exhibited a temperature 

 of 44 when the thermometer in the external air only registered 15. This 

 was at the period of the opening of the spathe, which was noticed at the 

 time to give forth a peculiar fragrance, like wine. Here, then, we have 

 a plant the temperature of whose respiring flowers exceeds that of blood- 

 heat ! 



The evolution of light from plants is also thought to be connected more 



