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JOSHUA ROSETT 



that the loss of substance has been bridged over by new growth 

 and that the stems are much thickened in that situation. Exami- 

 nation of the interior of this thickening shows two canals (see 



Fig. 3, A. A sketch from a photograph of an osmotic sac. Gas bubbles are 

 seen to adhere. Below and to the right is seen an aborted beginning of a stem 

 enclosing a gas bubble within its opening. Fig. B. Sketches made from photo- 

 graphs. 1, Gas bubble caught in the open tip of the stem. 2, The thickening of 

 stem at the point where the gas bubble is held. 3, The outgrowth of a branch 

 beneath the obstructing gas bubble. 4, The lining of the canal of the stem 

 enclosing a gas bubble. Magnification of 1, 2, 3 36 diameters, magnification 

 of 4 150 diameters. C. The effect of high temperature upon the osmotic growth. 

 D. Showing a thickening at the point where repair has taken place after fracture. 

 The black patches to the right of 1 are chips from the fracture which adhered 

 to the slide while it was photographed. 2, The interior of 1, showing the exact 

 site of fracture where the canal is interrupted. The new canal arises from the 

 side. Magnification 36 diameters. 



