158 Transactions of the [Sess. 



non-nitrogenous fluids cause them to secrete freely. The secretion in 

 this case, however, is not acid. Nitrogenous substances, on the other 

 hand, cause an mcreased flow of the secretion, which is invariably- 

 acid, and in this state it has the power of digesting insects or other 

 animal matter. Before absorption of animal matter, the glands are 

 green ; but after that takes place, the protoplasm contained in them 

 becomes aggregated, and of a brown colour. 



Nepenthes. 



The species belonging to this genus are upwards of thirty in num- 

 ber, and are, with a few exceptions, natives of swamps in the hotter 

 parts of the Asiatic archipelago. They are half-shrubby plants, and 

 climb by the aid of their leaves, which have the power of coiling or 

 twisting themselves round supporting objects. The leaves are meta- 

 morphosed as flattened expansions, Avhich narrow into long tendril- 

 like bodies, at the extremities of which the pitchers are developed. 

 These pitchers are often highly coloured, and generally contain a fluid, 

 into which insects, and sometimes even small quadrupeds or birds, 

 find their way. The pitchers vary in size from an inch or two to 

 nearly a foot in length, and one species at least has them no less than 

 eighteen inches long. 



The minute structure of the interior of the pitcher is of a very 

 complicated nature. It presents three distinct surfaces. The first is 

 the " attractive " surface, which occupies the inside of the lid and the 

 mouth of the pitcher. The inside of the lid is in most species stud- 

 ded over with honey -secreting glands. These consist of masses of 

 cells embedded in depressions of the cellular tissue of the lid, and 

 each is surrounded by a ring of guard-cells. Eound the mouth of the 

 pitcher is a corrugated rim, which projects into the cavity, and which 

 helps to keep the mouth distended, and the corrugations are often 

 prolonged as sharp downward-directed teeth. Hooker observed that 

 the rim secreted honey; and it has been discovered recently by Pro- 

 fessor Dickson that a circlet of glands is present in it. These glands 

 alternate with the corrugations of the rim, and open into the pitcher 

 a little above its loAver edge. They are of enormous length (in some 

 cases xV of an inch) compared with the other glands found in 'the 

 pitcher, but are comparatively narrow. They are embedded in the 

 tissue of the rim, and open into the pitcher cavity by short canals. 

 Next comes the " conductive " surface, which occupies a variable 

 portion of the upper part of the interior of the pitcher. This surface 

 is composed of smooth glassy cells, which afford no foothold to insects, 

 and it is generally studded over with minute reniform or crescentic 

 ledges. The remainder of the interior of the pitcher is occupied by 

 the " secretive " surface. This is thickly covered with glands resem- 

 bling those of the lid, but the depressions in which they are lodged 



