PROTOPLASMIC MOVEMENT. 391 



Kuhne i allowed Tradescantia hairs to freeze to the walls of 

 a platinum vessel without adding water. It was quickly low- 

 ered to a temperature of —14° C, and allowed to remain for 

 more than five minutes at this temperature without death of 

 the protoplasm ensuing. Taken out and quickly examined in 

 water, no trace of protoplasmic network was present, but the 

 violet interspaces in the cells presented near the naked nucleus 

 a great number of separated round droplets and little lumps. 

 A few seconds later these began to exhibit exceptionally active 

 amoeboid movement. After some minutes they began to run 

 together into single larger droplets, and these, again, united 

 with other groups, and in about ten minutes the original pro- 

 toplasmic network was there again ; and even after twenty- 

 four hours the threads were found in active streaming. 

 Hofmeister " has corroborated these observations. 



2. Imbibition "Water. 



The amount of imbibition-water acts like the degree of tem- 

 perature. For every protoplasm there is a maximum and mini- 

 mum for the amount of contained imbibition water at which 

 spontaneous movements stop. Exact determinations have not 

 been made, but the minimum may be stated as on the average 

 below 60 per cent, and the maximum over 90 per cent. 

 Within these limits the activity of the protoplasm generally 

 varies, with a corresponding increase of volume and decrease of 

 refractive index, with amount of the contained imbibition water. 

 Rapid changes in the extent of concentration of the medium, 

 which induce rapid swelling or more especially shrinking, may act 

 like an excitation (see below). There is always an optimum 

 for the amount of imbibition water. 



When the maximum is gradually approached the protoplasm 

 takes on its simplest form (globules, varicosities, &c.). Re- 

 moval of the excess of water with indifferent substances (weak 

 sugar solutions, salt solutions, &c.) often reinduce the move- 



1 W. Kuhne, ' Unters. iiber das Protoplasma,' U. S. W., p. 100, et seq. 



2 W. Hofmeister, ' Die Lehre von der Pflanzenzelle,' p. 54. 



