500 DEVELOPMENT OF LIGHT AND HEAT. 



with the law of gravitation, unite together where a boring has taken place, and- 

 again form a compact mass in consequence of the regelation of the lower strata. 

 It has still to be mentioned that the green leaves of the Soldanellas, which lie flat , 

 below the snow and ice, becoming flaccid during the growth of the flowers, and that ■ 

 the reserve materials stored up in them are completely used up by the growing stem 

 and flowers. The green leaves then become wrinkled and perish, while new leaves 

 develop after the snow has melted. These provide themselves with reserve food in 

 order that in the next period of vegetation the growing stem and flowers may 

 be efficiently nourished. 



Here and there with the flowers of Soldanellas are found the young, but never- 

 theless yellowish-red, foliage-leaves of Polygonum viviparum, which grow up from 

 below into the ice, and occasionally melt holes in it close to the edge of the snow- 

 field. The white flowers of Ranunculus alpestris growing in company with the 

 soldanellas in the same habitat have, on the other hand, not attained to the capacity 

 of growing through the ice, and need as an incitement to growth a temperature 

 which is rather above 0° C; in consequence of which they always open their flowers 

 first in places from which the snow has vanished a short time before. 



The amount of the heat set free by the small flower-buds of soldanellas might 

 be estimated by the quantity of ice melted, but so many sources of error enter into 

 a calculation of this kind that the numbers obtained cannot lay claim to much 

 accuracy, and we must be satisfied with the fact, even although it is not verified by 

 figures based on a calorimetric experiment. 



The melting of the ice by the heat liberated in the respiration of soldanellas is 

 also of the greatest interest, since it furnishes a proof that single, small, extremely 

 delicate flowers warm not only their own tissues but also their environment, and 

 that the heat liberated in them does not become perceptible only because, as already 

 remarked, it is counteracted by evaporation and radiation which are carried on at 

 the same time, and because the respiring flowers are usually surrounded by atmo- 

 spheric air, i.e. by a medium which is movable, fluctuating, and unstable. The 

 air which in one moment is warmed by the respiring leaves is carried far away in 

 the next instant, and is replaced by other air. This is the case especially in shallow 

 flowers with recurved leaves, or in salver-shaped corollas widely opened above, round 

 which there cannot be said to be any stagnation of air. But if the flower has 

 the form of an inverted bell, as in the Foxglove, Gloxinias, and most campanulate 

 flowers; if the floral-leaves bend upwards like a helmet, as in the Monkshood; if 

 the flowers are tubular, inflated at the base like a flask, or pitcher-like as in 

 Aristolochias, or form deep goblets as in the Cactaceae and many gourds — then the 

 air in the inclosed space is scarcely at all disturbed, there is stillness within the 

 flower, the air there collected and warmed is retained almost unaltered in its quiet 

 comer, and is not very easily replaced by other air. 



On cool days a rise of temperature above that of the surrounding air can be 

 usually perceived in the interior of such flowers, even when they stand quite alone. 

 In an Alpine meadow the interior of a flower of Oentiana acaulis in the morning 



