470 SCIENCE PROGRESS 



structed on several different principles. Those which depend 

 upon the complex interaction of conditions in the living proto- 

 plasm have not received and probably are not likely soon to 

 receive a full explanation ; but the more purely physical processes 

 involved in the other two classes have lent themselves to a closer 

 analysis, though, if closely regarded, the latter also will be seen 

 to contain within themselves the jealously guarded secret of the 

 how and why of their adaptedness to those functions which they 

 are so well fitted to discharge. Indeed, from this point of view, 

 perhaps they may even seem to be more difficult of compre- 

 hension than are those which result from the response of the 

 living protoplasm to definite stimuli. For the structure on 

 which the discharge of their functions depends has already been 

 determined by conditions which were operative in the protoplasm 

 at a period long anterior to that when the actual mechanisms 

 become of specific use. 



In fact the baffling problems of adaptation and adaptedness 

 are just as real and just as exigent of solution in connection with 

 the origin of the motile mechanism of a moss peristome or elater 

 of a liverwort as they are in any of the other numerous mani- 

 festations of protoplasmic activity. 



Bibliography 



[This bibliography is by no means exhaustive, but will enable any one desirous 

 of pursuing the subject further to do so.] 



DlNGLER, H., Die Bewegung der Pflanzlichen Flugorgane, Miinchen, 1889. 

 Dixon, H. H., and Joly, J., On the Ascent of Sap, Phil. Trans. Roy. Soc. 1895. 

 FARMER, J. B., On the Mechanism of Opening and Closing in Tulip Flowers, 



New Phytologist, 1902. 

 GOEBEL, K., Archegoniaten Studien (Nos. 6 and 7), Flora, Bd. 80 (1895) ; (No. 9), 



Flora, Bd. 88(1901). 

 Haberlandt, G., Physiologische Pflanzenanatomie, 4te Aufl., Leipzig, 1909. 



■ , Sinnesorgane im Pflanzenreich, 2te Aufl., Leipzig, 1906. 



Kammerling, Z., Zur Bewegungsmechanismus der Lebermooselateren, Flora, 



Bd. 85 (1898). 



, Oberflachenspannung u. Cohesion, Bot Centralbl. Bd. 75 (1898). 



LEPESCHKIN, W. W., Zur Kenntnis des Mechanismus der photonastischen Varia- 



tionsbewegungen . . ., Beih. Bot. Centralbl. Bd 24 (1909). 

 Lillie, R., The Relation of Stimulation and Conduction in Irritable Tissues to 



changes in the Permeability of the Limiting Membranes, Am. Jour. Physiol. 



vol, 28 (1911) 

 LoRCH, L., Einige Bewegungs- u. Schrumpfungserscheinungen an den Achsen u. 



Blattern mehrerer Laubmoose als Folge des Verlustes von Wasser, Flora, 



Bd. 97 (i9°7). 



