498 DEVELOPMENT OF LIGHT AND HEAT. 



develop very rapidly to a considerable size, and connected with this rapid growth 

 there is always a rapid movement of the food absorbed by the mycelium, com- 

 bined with an energetic respiration. Respiration is carried on chiefly at the 

 periphery of the receptacle — in the mushrooms especiallj- in the hymenial layer, 

 which is veiy well protected from evaporation and radiation by its position on 

 the lower side of the cap. Transmission of the food, and in particular of a large 

 amount of water, takes place thi-ough the stalk which bears the cap. Numerous 

 observations of fungi gi-owing in their natural free condition, and rising but 

 little above the soil, have invariably sho\A'n this result: the rise of temperature in 

 the tissue of the cap is most pronounced where respiration is carried on most 

 actively, i.e. in the lij-inenial laj-er. It is less in the central portion of the cap, 

 and least in the stalk, through which the watery fluid travels at a temperature 

 which difiers but slightly from that of the surrounding earth. Respiration, of 

 course, cannot be considerable here. For example, in Boletus edulis, from its size 

 and shape particularly well suited for these investigations, the following results 

 were obtained while the temperature of the surrounding earth was about 13° C. : 

 temperatui-e of the stalk, 14-2-1 5-6°: temperature of the bodj^ of the cap, 15'2-16-8°; 

 of the hymenial layer, 167-181\ Fui-ther developed (but still quite fresh) fructi- 

 fications exhibit higher temperatures than youuger oues which have just appeared 

 above the ground. Observations on other fungi of the H\'menomycetes j-ield like 

 results. When the temperature of the surrounding earth was 12-2° Ladarius 

 scrobiculattcs exliibited in its stalk a tempei-ature of 148°, and in its cap of 160°; 

 Amayiita miiscaria in its stalk 142°, and in its cap 15'2°, while the temperature 

 of the surrounding soil was 130'; Hydnum imbricatum, 130° in the stalk and 

 14'5° in the cap, while the surrounding eai-th showed a temperature of 122°. The 

 peculiar shape of the cap in these last-named fungi is not well adapted to a 

 separate measurement of the temperature in the body of the cap and in the 

 hjnnenial layer, but it is probable that a slight difference exists between them, 

 similar to that found in Boletus. The pufl-balls belonging to the GasteromA-cetes 

 also exhibit a considei-able rise of temperature above that of their surroundings 

 in the respiring portions of their fructifications. Thus in Lycoperdon ccdatum a 

 temperature of 158' was observed in the sjjherical receptacle shortly before dehis- 

 cence, while the temperature of the surrovmding soil was onlj- 12'2°. 



The liberation of heat appeai-s especially noticeable, too, in respiring flower-buds 

 and in the mpidly-growing stalks which bear them, as well as in opened flowers. 

 If the flowei-s are small, and if there are but few of them at the end of the stem, 

 or if ouh' a single small flower is boi-ne at the end of a dehcate stalk, the heat 

 liberated may easily escape observation: but under very favoui-able conditions it 

 makes itself readily manifest, and gives rise to a phenomenon so strange and 

 unintelligible that everyone on observing it for the tii-st time is sui-prised and 

 puzzled. I refer to the fact that small and delicate flowei-s gix>w buried beneath 

 the snow, and obtain the space they require by melting the hardened snow. The 

 Alpine Soldanella is a very marked instance in point. As the snow melts and the 



