398 



MOVEMENTS. 



live wholly in the water, as the algse, have the power of inde- 

 peiideiit locomotion. This is exhibited strikingly in the motile 

 spores, which are provided with cilia, and can thereby propel 

 themselves fi'om place to place with considerable rapidity. Sim- 

 ilar independent motion is shown also by the antherozoids of 

 many of the lower and even some of the higher cryptogams. 



The protoplasmic movement by which such locomotion is 

 secured is essentially identical with certain ciliary movements 

 observed in the animal kingdom. 



1039. It is a familiar fact that some minute algse, furnished 

 either with walls of cellulose (Desmids) or cellulose impregnated 

 with silicic acid (Diatoms), possess the power of motion, but 

 the cause is not well understood. In the case of the skiff-shaped 

 diatom the motion is somewhat spasmodic, and the course of 

 the organism through the water is not in a straight line, but it 

 is nevertheless enabled to traverse a considerable distance in a 

 short time. Owing to the absence of an}- distinct cilia, it is 

 difficult to conceive the mechanism of propulsion. According to 

 Max Schultze there is a minute slit on 

 the under side of tlie motile diatoms, and 

 through this slit a delicate film of proto- 

 plasmic matter projects. By contact of 

 this motile film with surrounding objects, 

 the diatom, as it is sui)ported in the 

 water, is transported from place to place. 

 These three cases of locomotion, name- 

 ly, of (1) naked protoplasm, (2) of ciliated 

 structures, (3) of apparentl}- closed cells, 

 do not exhaust the list of instances of 

 motion of vegetable organisms from place 

 to place ; other cases are referred to the 

 succeeding volume upon the lower plants. 

 1040. The movement of protoplasm with- 

 in cell-walls has already been sufficiently 

 examined (see 646) ; but attention should 

 now be called to the fact that chlorophj'll 

 granules (which are always embedded in 

 the protoplasmic mass) frequently assume 

 at night, or when a portion of the leaf is 

 darkened, positions different from those 

 which they have during strong exposure to light. This change 



Fio, 175. Circulation of protoplasm in hair of Gotfrd. (Sachs.) 



