72 CARNEGIE INSTITUTION OF WASHINGTON. 



syneretic cavities disappear and the laminated structure appears in 

 its place. 



In the Uving tissues the mucilage masses and the surrounding 

 parenchyma cells are in unstable equilibrium, the hydration capacity 

 of the mucilage being great enough to withdraw more or less water 

 from the adjacent cells. When water is allowed access to the tissues, 

 some mucilage cells may burst. The same result may be obtained by 

 causing the loss of water from the parenchyma by asphyxiation. 



The rather abundant mucilage of Oenothera occurs within the proto- 

 plasmic utricle (in contradistinction to the foregoing forms) in elon- 

 gated fusiform cells which are raphid idioblasts. It also is precipitated 

 in situ by ruthenium red, the whole becoming flocculated and under- 

 going syneresis to form a nematoid mass. When exposed to neutral 

 red (acid solution) the stain is first adsorbed in the interior of the 

 mucilage in the neighborhood of the raphids, the affected volume 

 then extending radially in all directions. At first the adsorption com- 

 plex usually occurs in the form of interwoven threads of very minute 

 caliber, which, with thickening, ultimately form a flocculent mass. 

 Both stains slowly render the mucilage insoluble. 



The Colloidal Properties of Certain Plant Mucilages as affected by Stains, 



by Francis E. Lloyd. 



The writer has often observed that when substances such as the 

 mucilaginous products of the hydrolysis of cellulose walls which 

 occur during abscission, the ripening of fruits, etc., are treated with 

 certain staining materials, a quasi precipitation occurs. Recently it 

 was found that ruthenium red causes the formation of insoluble 

 membranes on the surface of Opuntia mucilage. Following this lead 

 the effects of a considerable series of dye materials on the mucilage of 

 Opuntia, Abutilon, Oenothera, peach pericarp, and the products of 

 cell-wall hydrolysis during abscission were studied. 



It was found that some stains (e. g., neutral red, ruthenium red) 

 slowly reduce the viscosity of hydrated mucilages until their physical 

 properties as emulsion colloids entirely disappear. These stains are 

 adsorbed with great vigor. On the other hand, some stains (e. g., 

 corallin, methyl orange) are not adsorbed at all and have no effect 

 on the viscosity or hydration capacity of the mucilage. Still other 

 stains (e. g., methylene blue) are slightly adsorbed and at the same 

 time measurably reduce the viscosity. In general it may be said that 

 the viscosity of the mucilages in question is reduced by stains in direct 

 relation to the adsorption capacity of the mucilages for these stains. 



The Index of Transpiring Power of Plants, by Edith B. Shreve. 



As mentioned in last year's report,* the chance for the greatest error 

 in the use of the tripartite cobalt-paper slips for determining the in- 



* G arnegie Inst. Wash. Year Book for 1917, p. 68. 



