145 



yeast suspensions to a freezing tempei'alure of -9°, states 

 thai a witlulrawal of watei- was evidenced by a shrinking 

 of the cells (l)y a])Out 10'/<' of the original volume) and by 

 the fact that the vacuoles became indistinct. The cells 

 themselves, he thinks, nevei- froze. 



The same author described also an exudation of water 

 from various filamentous algae: Spirogyra, CladopJiora, 

 Derbesia, etc., observed under the microscope during the 

 congelation of their medium. In a Spirogyra the diameter 

 decreased by 62 9^ . Then he froze these algae in olive oil 

 and noticed that the extruded water formed a cylinder of 

 ice around the plants. In some forms the ice exuded pre- 

 sented a characteristic filamentous pattern, with the fila- 

 ments sometimes twisted like in a screw, a pattern that he 

 also observed in moss leaves and in fern prothalia. 



In staminal hairs of Tradescantia, Matruchot and Mol- 

 liard (1902) observed, during freezing, a loss of turgor, a 

 decrease in cell volume comparable to that which occurs 

 in plasmolysis, and a decrease or disappearance of the 

 large vacuoles. They consider all these features as result- 

 ing directly from the withdrawal of water. 



8. Cellular ('o)istituents. AVliile the preceding investi- 

 gations refer to the exudation of water from freezing cells, 

 Matruchot and Molliard studied the evidence of with- 

 drawal of water from the cell constituents, in particular 

 from the nucleus. Plant tissues of various types w^ere left 

 to freeze for several hours (15 hours mentioned in one 

 case) at temperatures from -4° to -7°; then they w^ere 

 thawed, fixed and stained. The authors used cells with a 

 somewhat abundant vacuolar content taken from the lacu- 

 nar parenchyma of the leaves {Narcissus), from the cortex 

 of the hypocotyl axis {Phaseolus), from the stem {Lupi- 

 nus), from the parenchyma of the roots {Hyacinth us), 

 from the floral peduncles {Clivia, Tulipa), and also cells 

 of more compact cytoplasm, such as those found in the 

 tissues of the nucelle {Leucoium) and of the ovary {Tu- 

 lipa). The essentials of their results are represented in 

 Figure 15. The nucleus, homogeneously granular in un- 



