THE MANIFESTATIONS OF LIFE 



51 



in search of moisture. If, however, they are artificially 

 so arranged that the source of moisture is above, the 

 rootlets turn up instead of down in order to obtain it. 



The hyphomycetes or moulds which require much 

 moisture for successful growth, when cultivated in a 

 bottle containing a few drops of liquid, are found to 

 conform in distribution to the moisture of condensation 

 upon the sides of the glass. 



The hydrotropic behavior bears some relation to the 



FIG. 8. " Barentierchen." This animalcule is capable of resisting the ill 

 effects of loss of water, a. The active animal. 6. The same in the dry state 

 and apparently dead. When moistened, it absorbs water and resumes its 

 active form again. (After R. Hertwig.) 



developmental stage of the organism; thus in the myxo- 

 mycetes the positive hydrotropic reactions continue 

 only during the vegetative stage and so soon as the 

 fructification begins, and it is desirable to keep the 

 sporangiophores dry, negative hydropism begins and 

 the reactions are reversed. 



Loss of moisture and consequent inability to main- 

 tain activity leads to a variety of manifestations among 

 both animals and plants. Among the most lowly 



