278 COMPENDIUM OF GENERAL BOTANY. 



known.' Cells of tlie Characece show the streaming movement 

 of plasm very beautifully. 



With these general remarks on some of the more important 

 movements met with in the vegetable kingdom we may group 

 them, according to cause, as follows. 



1. Locomotor movements due to causes inherent within the 

 protoplasm. It were better to say that the cause or causes are 

 unknown. 



2. Purely mechanical movements due to variations in the 

 turgor of living cells or to absorption or loss of water by dead 

 cell-walls. We will name them collectively " hygroscopic " 

 movements. 



3. Autonomous or spontaneous movements, often producing 

 extensive changes in form and position, are also due to internal 

 causes, such as processes of growth. 



4. Irritable movements (induced movements). 

 We will briefly discuss movements 2, 3, and 4. 



B. Hygroscopic Movements. 



The term hygroscopic applies to the unequal gain and loss of 

 water by dead as Avell as by living cells. Under the category of 

 hygroscopic movements belong the opening of sporangia and 

 anthers as well as fruits for the purpose of ejecting the seeds, 

 spores, etc. A number of these cases have been elucidated by 

 the investigations of Schinz, Schrodt, Zimmermann, Steinbrinck, 

 EiCHHOLZ, ZoPF, and others. Since these movements have 

 already been more or less explained in the chapters on repro- 

 duction, I will here limit myself to the following statement. 

 Hygroscopic movements are usually due to the difference in the 

 power of imbibition possessed by the various tissues and tissue- 

 layers. Visible structural differences often indicate the differ- 

 ence in the power of imbibition. The dynamical cells evidently 

 come into play here (Zimmermann). These cells have a moder- 

 ately thick wall, with approximately horizontal rows of micellae 

 which are capable of shortening considerably on drying, much 



' Attempts have been mude by various investigators to explain the plienoniena 

 of protoplasmic movement, but so far not very successfully. Ghemism and surface- 

 tension of liquids are perhaps factors in such movement. See Berthold's Proto- 

 plasmamechanik. — Trans. 



