PITCHER-PLANTS. 113 



zone, and 36 in the lowest. So that, where the 

 diameter of the glands only ranges between '045 

 and 'oy mm., the number is 73 in a given space 

 (one square millimetre) ; but when the glands are 

 •135 to - I9 mm. in diameter, or twice to nearly three 

 times as large, there are only one-third of the number, 

 or 25, in the same area. 



In the upper zone (of Nepenthes Rafflesiana), where 

 the glands are small, though numerous, they are 

 wholly covered by the hood. " The complete cover- 

 ing of the glands in this zone," writes Dr. Lawson 

 Tait, 1 " may be of advantage in protecting them and 

 their secretion from accident and the depredation of 

 insects, for the glands here are much more likely 

 to be uncovered by water than those further down. 

 I think it is also very likely that these hoods store 

 up the digestive principles of the pitcher until they 

 are required, or until it is washed out by the contact 

 of water, it being retained in their cavities by capil- 

 lary attraction." 



" In the second zone the glands gradually alter 

 from a round shape to an oval one, increasing at the 

 same time in size as they are viewed from above down- 

 wards, and they become less covered by the hoods. 

 The relative gland area is also greatly increased. 

 The greatest amount of work would necessarily fall 



1 " Midland Naturalist," March, 18S0, p. 62. 

 I 



