10 BOTANY. 



perature of 20° C. to one of 30° C. (68° to 86° FaUr.V. withdraws its pseud- 

 opodia and ceases its activity in tlie space of five minutes. In an hour 

 after the restoration of the normal temperature (20° C.) tlie movements 

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

 organization of the Plasmodium is destroyed. 



The Plasmodium of Fidigo va/rians, Sommf. (^ilialium septicum. 

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

 rounded form and I eases all mo lion ; upon gradually raising the tem- 

 perature again the normal state is resumed. 



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

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

 Plasmodium contracts, and becomes rounded and motionless. A sudden 

 decrease in the concentration of the solution by whicli a Plasmodium 

 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 ehow 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 ci-ovvn about 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 Myxomycetes have but one. 



The rapidity of the swimming motion produced by cilia is consider- 

 able, as shown by measurements made by Hofmeister* in the case of 

 swarm-spores, viz. : 



Puligo -Dorians (^thalium septicum). .. .7 to .9 mm. per second. 



Lycogola epidendrum .88 mm. " " 



QHdogonium msicatum 15 to .30 mm. " " 



Vaucheria 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 such as 

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



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



