10 BOTANY. 



perature of 20 C. to one of 30 C. (68 to 86 Fahr.) ; withdraws its pseud- 

 opodia and ceases its activity iu the space of five minutes. In au hour 

 alter the restoration of the normal temperature (20 C.) the movements 

 begin again. If the temperature is raised to 35 C. (95 Fahr.) the 

 organization of the plasmodiuni is destroyed. 



The plasmodium of Ftdigo variaiis, Sommf. (^tltalinm septicum, 

 Fr.), when placed in a chamber surrounded by ice, contracts into a 

 rounded form and ceases all motion ; upon gradually raising the tem- 

 perature again the normal state is resumed. 



(d) In glycerine, a concentrated solution of sugar, a five per cent solu- 

 tion of potassium nitrate, or a five per cent solution of sodium chloride, a 

 plasmodium contracts, and becomes rounded and motionless. A suddi-u 

 decrease in the concentration of the solution by which a plasmodiuni 

 is surrounded also results in a stoppage of its movements. A plasmo- 

 dium of Didymium serpula, when placed in a one per cent solution 

 of potassium nitrate, and allowed time to regain its activity, suddenly 

 rounds itself up and stops its movements when the preparation is 

 washed out with distilled water ; after the lapse of a few minutes (ten 

 to twelve) the activity begins to show itself again, and in half an hour 

 the normal state is restored. 



10. Ciliary Movement. The swimming of swarm-spores, 

 spermatozoids, and many other naked protoplasmic bodies, is 

 due to the rapid vibratory motion of extremely small whip- 

 like extensions of the hyaline portion of the protoplasm. 



Examples of ciliary movement are very common. In some swarm- 

 spores, as in those of Vaucheria, the whole surface is covered with short 

 cilia ; in others, as in (Edogonium, the cilia form a crown al.out the hya- 

 line anterior extremity ; those of Pandorina and Cladophora, and the 

 spermatozoids of Bryophytes and Pteridophytes, have two or more cilia ; 

 while the swarm-spores of Myx<>mycetes have but one. 



The rapidity of tli e swimming motion produced by cilia is consider- 

 able, as shown by measurements made by Hoi'meister* in the case of 

 swarm-spores, viz. : 

 Fttliyo varians (^ffithalium septicum). .. .7 to .9 mm. per second. 



Lycogola epidetidrum .33mm. " 



(Edogonium tesicatum 15 to .20 mm. " " 



Vancheria sp 10 to .14 mm. " " 



1 1 .The Activity of Protoplasm Enclosed in a Cell- wall. 

 The movements of protoplasm in closed cells differ but 

 little from those in naked ones ; the differences are sucli as 

 are due to the fact that in the latter case the protoplasm is 



* " Lehre von der Pflanzenzelle," p. 30. 



