Sentence:  When studying the <WSD>nepenthes</WSD>, I was puzzled to see the use of the channel which exists on the back of the pitchers, and which is formed by two ridges furnished with spikes in most of the <WSD>nepenthes</WSD>, but not in all, which run up to the margin of the lip of the pitcher. 
Meaning of the word marked with <WSD> tags:  A Southeast Asian carnivorous plant of the genus "Nepenthes"; a monkey cup or tropical pitcher plant.