IQ02 ] CURRENT LITER A TURE 243 



they are), it appears that active movements of stomata are much more com- 

 mon than we have been led to believe. And the method of opening and 

 closing, apparently always dependent upon an osmotic change in volume of the 

 guard cells, is as various as are the plants in which it occurs. Absorption of 

 water with its accompanying increase in the volume of the guard cells results 

 in so altering the shape of these cells, by bending or stretching their walls, as 

 to open the pore between them. The mechanical types of stomata studied 

 are illustrated by figures and are tabulated hy the author in the following 

 scheme, which is copied froui his concluding paragraph. *'The pore opens by 



1. A change in shape, rather than by stretching the walls, in which the 

 change is 



{a) An increase in the depth of the guard cell, in which there is chiefly 

 concerned the entire wall except the dorsal (Medeola, Equisetum), the 

 inner half (Mm"um), the outer half (Funaria), the dorsal half (Lycopodium), 

 the ends (Osmunda). 



(^) An increase in the width of the slender stoma (Sagittaria). 



2. Stretching the thin dorsal wall (Amaryllis). 



3. A change in shape, with or without much stretching, at the ends of the 

 guard-cells, which forces the dorsal wall, with the passive middle part of the 

 cell, either directly backward (Gramineae), or upward and backward (Coni- 

 ferae). 



4. Combinations of the types of Amaryllis and Mnium (Helleborus), and of 

 Amaryllis and the Gramineae (Achil)ea).*'^ B. E. Livingston. 



Spindle formation in Agave americana has been described recently 

 by Osterhout.-® Considerable attention was given to technique, especially to 

 fixing. About forty fixing agents were tested by watching their effect upon 

 the living cell, and it was found that some of the most highly recommended 

 solutions produced profound disturbances in the cytoplasm. For most objects 

 fixing agents were found which produced no visible change in the living cell, 

 as far as could he observed with a 2"'"* oil immersion lens during the applica- 

 tion of the reagent ; but even in some such cases the material undergoes 

 structural changes after a few hours, and the time must be shortened accord- 

 ingly. Flemming's strong mixture proved to be the best in most cases; very 

 fair results were obtained with iridium chloride, platinum chloride, palladium 

 chloride, and Flemming's strong mixture with an excess of chromic. Material 

 was washed from two to eight hours in running water and then dehydrated. 

 Mixtures of absolute alcohol and bergamot oil were used for clearing. Gen- 

 tian violet was used for staining kinoplasm. If the stain washes out too read- 

 ily, some gentian violet should be dissolved in the absolute alcohol. From 

 two to twenty seconds' immersion in dilute iodide iodine solution just before 

 transferring to the absolute alcohol often gives a sharper differentiation. 



^OSTERHOUT, W. J. v., Cell Studies. I. Spindle formation in Agave. Proc. Cah 

 Acad. Sci. III. 2: 255-284. ph. 23-28. 1902. 



