152 FRANCIS E. LLOYD AND CHARLES S. RIDGWAY 



metamorphosis as a source of sugars which, by virtue of their 

 position without the gland, furnish the conditions for the further 

 withdrawal of water, has been suggested by Pfeffer. 7 This same 

 condition might very well be thought as acting to cause a change 

 in the condition of the protoplast whereby the semi-permeability 

 of the plasmatic membrane to sugars would be altered, and so 

 make the exosmosis of sugars possible, since the actual excretion 

 of these substances, in addition to that of water, does take place. 8 



The cases before us furnish additional examples of a type of nectar 

 gland in which the excretion of sugars (and of other substances 

 in less quantities) is preceded by the breaking down of one or more 

 cells. The prototype is that curious nectar gland described by 

 Zimmerman 9 in one of the tropical Loganiaceae, Fagraea. In 

 this gland the branching duct results from the breaking down of 

 the so-called "protoderm" cell, only after which, it would seem, 

 the secretion of nectar commences. It is entirely probable that 

 the operation of thus forming the duct results in a supply of osmoti- 

 cally active substances comparable to those which are present in 

 the nectar-gland of the Cactaceae in consequence of the digestion 

 of the epidermis. It may be further argued with certainty that 

 the first fraction of the exuded nectar would be found to contain 

 a greater proportion of proteins than the latter. 



A further example has recently been described very briefly by 

 Dummer 10 in Platy cerium, in the fronds of which lysigenous 

 pockets are formed, either beneath the epidermis or involving it. 

 In the latter case, the condition simulates that which we have 

 described. It is not clear from Dummer's account that tne exudate 

 escapes without a breaking down of the epidermis. In the event 

 that it does, it seems more likely that the stomata furnish a path 

 of escape than that it passes through the walls of the unchanged 

 epidermal cells. 



7 Physiology of plants, 1 : p. 283. 



8 On this see Livingston, B. E., The role of diffusion and osmotic pressure in 

 plants. Chicago, 1903. 



9 Through Haberlandt, Ph'ysiologische Pflanzenanatomie, 4th ed., p. 462. 



10 Dummer, R., Grape sugar as a secretion in PZa^cerfu/n. Ann. Bot.,25: 1205- 

 1206, Oct. 1911. 



