DEPARTMENT OF BOTANICAL RESEARCH. 71 



The Mucilage of Opuntia, Ahutilon, and Oenothera, hy Francis E. Lloyd. 



The opuntias and mallows contain a mucilage having a very high 

 hydration capacity, as is shown readily by placing pieces of tissue in 

 water, when the material in question swells to form a ropy mass of 

 high viscosity. It occurs in relatively large cells which arise by 

 idiosjTicrasis from parenchyma cells and only in minor extent from 

 embryonic tissue. In Opuntia they are distributed in the medulla 

 and in the cortex, in some species (Opuntia discata) coming very 

 close to the hypodermis, and in others leaving a considerable zone 

 of chlorenchjina free from them {Opuntia hlakeana). When sections 

 from such kinds are judiciously cut parallel to the epidermis and 

 placed in water, no escaping mucilage may be detected. In Ahutilon 

 the mucoblasts occur chiefly in the stem, pericarp, and coroUa. The 

 structure of these cells is identical in both. The mucilage arises from 

 the inner zone of the cell-wall. This, during the early development of 

 the mucoblast, when it enlarges greatly, shows no chemical divergence 

 until the mucilage begins to be formed, when it gives in its inner 

 zone the hydro-cellulose reaction. The accumulation of mucilage, 

 together with its hydration, results in the gradual contraction of the 

 protoplast in the middle of the cell, its connection with the original 

 cell-wall being frequently sustained by radiating strands which at 

 their outer ends are attached to the pits connecting with adjacent 

 cells. With age the protoplasm becomes disorganized and partially 

 obliterated, there remaining only thread-like traces. 



The adsorption capacity for staining colors (and other substances) 

 is of peculiar interest. Here may be mentioned particularly two 

 cases. Neutral red is adsorbed from a neutral or slightly acid, but 

 not from an alkaline solution. The staining is not, however, selective, 

 since it is also taken up by the cellulose, oil, annulse of the xylem, etc. 

 When partly hydrated mucilage is placed in stronger neutral red, the 

 hydration is arrested and the color is adsorbed with extreme aridity. 

 Ruthenium red (as Uttle selective as neutral red) precipitates the 

 mucilage and wall, in the course of some days, render the mucilage 

 in situ incapable of further swelling even in boiling water. The mucil- 

 age masses are then evidently coagulated and break under pressure in 

 the manner of coagulated tannin masses, as described by the writer. 



jVIany other stains are adsorbed feebly and with little or no coagu- 

 lating effect, while still others not at all, and these have no effect 

 on the hydration capacity of the mucilage. 



WTien the tissues are dehydrated, as by alcohol, the mucilage masses 

 undergo internal syneresis, minute cavities occurring in more or less 

 regular zones alternating wdth homogeneous zones. This was found 

 to be due to the different degrees of hydration of these zones, cor- 

 responding to a laminated structure, seen by Longo, resulting from 

 the mode of origin of the mucilage. On the addition of water, the 



