no MINUTE STRUCTURE. [chap. 



Pulp of any ripe fruit. Large, thln-walled cells. 



Pith of a young branch of any tree. The cells are often 

 closely packed, and consequently polygonal. 



Piece of the stone of a stone-fruit, or shell of a nut, as 

 Cocoa-nut, ground excessively thin, by rubbing it with the 

 finger upon a hone. The cells have very thick sides, so 



Fig. 88. Cellular tissue, with the walls of 

 Fig. 87. Thin-walled cellular the cells much thickened, as in the stone 



tissue of pith. of stone-fniits. 



thick that sometimes the cavity is almost obliterated. The 

 " pores " are lengthened out into long " canals," which 

 radiate from the cavity of each cell. 



Yam. Potato. Thin-walled cells. 



Young shoots of any Fern (boiled to a pulp). Large 

 vessels, marked with cross bars. 



Pine-wood (thin slices, both lengthwise and across the 

 " grain "). Long, thick-walled, tapering cells, without any 

 vessels. The sides of the cells are marked with minute 

 disks. 



Thin petals, and petals doubled back to show the pro- 

 jecting cells on the folded edge. 



Pollen. The grains are usually oval or roundish, and 

 generally separate. Compare the pollen of Hibiscus, Cu- 

 cumber or Gourd, Passion-flower, Lily, any Convolvulus, and 



