HISTOLOGY OF PITCHER PLANTS. 161 



the central cell seems to be one bulging up from a somewhat lower 

 level between the 2-4 peripheral cells of the body which would 

 otherwise constitute a stoma-like opening." 



I am pleased to be able to confirm this conclusion of Dr. Dick- 

 son's, and to give a figure (Fig. 10) of one of these stoma-like 

 glands. That this central cell is glandular, I have no doubt — both 

 from its appearance and from the fact that, treated with aniline blue, 

 it takes the colour much more quickly and intensely than does the 

 surrounding tissue. 



Dr. Dickson, in conclusion, adds : — " If the above surmise be 

 correct, these bodies may be regarded as analogous to the ' Wasser 

 Spalten,' recently described by De Bary, in which case their secre- 

 tion would probably serve to dilute the other secreted matter ; to 

 which an interesting parallel might be found in the dilution of the 

 secretion of the urinary tubules by the water given off from the 

 Malpigian tufts of the kidney." 



In Cephaloiifs, as in the other sj^ecies described, there are special 

 appliances for preventing the escape of insects after they have once 

 entered the pitchers. In this sjDccies we have, first, the corrugated 

 rim, which is involute ; then a mass of tissue projecting downward 

 into the cavity of the pitcher, and having a sharp edge — this Dr. 

 Dickson calls the " conducting shelf " — affording, as it does, sj^ecial 

 facilities for the entrance of the insect, but assisting most effectually 

 to prevent its return. Below this there is a series of strong close 

 set hairs, the direction of which is still downward, and, together, 

 these three structures must present an insurmountable barrier to the 

 escape of the poor creature when once it has passed their lowermost 

 limit. 



With regard to the digesting powers of the plant, Dr. Tait 

 says : — " In two pitchers I found insects bathed in fluid with a 

 strongly acid reaction, and this fluid digested shreds of albumen 

 exactly as I found the fluid of Nepenthes pitchers did. I conclude, 

 therefore, that a true digestion of its victims is carried on by the 

 Cephalotus pitchers." 



We now come to our last genus. Nepenthes, in which the pitchers 

 are formed, not by the. transformation of an entire leaf, as on the 

 three genera already dealt with, but by the modification of the upper 

 portion of a leaf, a spine-like projection at the hinge of the lid 

 representing its true apex. In some species the whole, and in 

 others the greater part of the interior surface is covered with large 



