3IO WILLIAM SEIFRIZ. 



breaking before a perceptible indentation can be noted. Further 

 dissection gave convincing evidence that this membrane is a 

 morphologically differentiated layer. On breaking a globule 

 some of the liquid protoplasm escaped. The pellicle of the 

 ruptured mass stood out prominently and could be handled with 

 a needle as one would handle a hair. It was of no appreciable 

 thickness, yet quite rigid, though easily bent with no indication 

 of being soft or glutinous. It had, therefore, during dissection, 

 undergone a change the normal, and extremely sensitive mem- 

 brane had become a tough rigid gel. Such behavior well sup- 

 ports our interpretation of the plasmodium pellicle not a sur- 

 face-tension membrane nor a secreted wall, but a bounding layer 

 of denser protoplasm. The plasmodial membrane is, then, a gel 

 of appreciable thickness, tenacious, very extensile, contractile, 

 and glutinous. 



Next in importance to the possession of a definite morphologi- 

 cal membrane is the capacity for forming one. The evidence 

 which dissection work on myxomycetes presents on this phe- 

 nomenon is, briefly, that the membrane is instantly and repeat- 

 edly reformed when ruptured by a needle, provided the proto- 

 plasm is normal. This is true whether the dissection be per- 

 formed on a dry cover or in water; that is, the capacity is un- 

 changed whether air or water is the surrounding medium. If 

 gelation has set in the capacity for membrane formation is lost, 

 although it may persist surprisingly long. 



The living substance of slime-moulds is non-miscible in water. 



POLLEN TUBES. 



Of the many pollen grains experimented with those of the large 

 blue flag (Iris versicolor) were the most satisfactory. The grains 

 are large and germinate readily in almost any per cent, of sugar 

 solution. The pollen of the beach pea (Lathyrus maritimus) is a 

 fair substitute. 



Repeated irritation of a pollen tube puts an end to proto- 

 plasmic streaming, although in some instances streaming may 

 continue even after a tube has been punctured, and a large amount 

 of its contents lost. Streaming, however, is not accelerated by 

 irritation, nor is there any indication of a rush of protoplasm to 



