68 READINGS IN BIOLOGICAL SCIENCE 



ridge which swoops through the air thirty miles a second when the wind 

 freshens, and which is so far from the other clusters of needles that you 

 can not see them. VVe are alone in the wide sea of air — no place for reflect- 

 ing on an abstraction of biology. Doubtless you wish to get under cover. 



Hold fast while we crawl up the slope to one of the white spots that 

 extend in straight rows from base to tip of the needle. It is a hundred feet 

 away. We can reach it if we carefully watch our foothold and grip the 

 sticky knobs that dot the surface. 



So — here we are at the border of a pulpy square, forty feet wide, rising 

 five feet above the level of the surface of the leaf. It is heaving like a 

 breathing body. Follow me up the side of it and across it to the dirty look- 

 ing center. This one of the forty-eight thousand breathing-holes on the 

 needle. (Don't be astonished at that number; it is small because the pine 

 is adapted to a dry hfe. Some leaves have millions of breathing-holes.) This 

 hole is by no means a safe place, for the passage down through it will close 

 at any time when the leaf grows too dry; we might be caught and suffo- 

 cated. However, on this foggy morning the chances are good that the hole 

 will remain open. The diameter is more than a yard at the top. As we crane 

 our necks over the edge and peer down, we can see that the passage grows 

 more restricted below, but it looks wide enough for us to wriggle through. 

 Now you begin to realize that you were not made small enough for a 

 comfortable trip through a pine tree. I am going down head first, because 

 there is no fear of dropping into any deep cavern — the space in the needle 

 is close-packed with equipment. You may go feet first if you will feel 

 safer. 



For five feet I make a plunge, staying myself with outspread arms and 

 legs; then I squirm five feet more between the soft pulsing walls of the 

 funnel — and drop ten feet, as if I had broken through the ceiling of a room, 

 to a cushiony floor that feels like a rubber mattress filled with water. 



Of course this floor is a cell. Every place you can touch in all the height 

 and breadth of a tree is part of a cell. The floor is a breathing, hard- 

 working, intricate individual. In shape it is an irregular oblong, some fifteen 

 feet in width. VVe are sitting on the end of it — as if on the end of a great 

 sack of water that extends fifty feet in length toward the axis of the needle. 



As our eyes become accustomed to the dim light, we realize that we 

 are in a chamber about ten feet in diameter, formed by the ends of a dozen 

 or more cells. These are pressed tightly together — in fact they are prac- 

 tically grown together; for there are ducts communicating between them, 

 and they work as an organized whole. Here and there you can see that 

 between the cells there are passages wide enough for us to creep through, 

 but nowhere wide enough for comfortable walking. You should have al- 

 lowed me to make you smaller. 



If we gaze about a few minutes, taking in one feature after another of 

 this chamber under a breathing-hole, we begin to realize that we are in the 



