396 Field, Forest, and Wayside Flowers 



as we have seen, travels via the young wood ; elab- 

 orated sap moves through the inner bark or 

 " bast," where, in most trees, a way is prepared for 

 it through what are technically known as " sieve- 

 cells." These are long and narrow, and run length- 

 wise of trunk and boughs. 



As the sap moves through them, it comes to 

 places where the partition-wall between cell and 

 cell is "punched full" of holes, like the top of 

 a pepper-pot. Fine fibrils of plant-jelly reach 

 through these, joining the contents of neighboring 

 cells, and in summer, plant-fluids pass easily all 

 along the route. But as autumn approaches, Nature 

 seals these holes and isolates the " sieve-cells." 



About midsummer, a glutinous plate, called the 

 callus-plate, begins to form upon the little sieve, 

 stopping up its pores. This gains thickness and 

 solidity all through the waning of the year, and by 

 time the leaves fall the route through the sieve- 

 cells is closed as completely as is the route to Klon- 

 dike in midwinter. This sealing of the little 

 sieves has a beneficent purpose. At almost any 

 time throughout the winter, in our latitudes, we 

 may have a false promise or mocking similitude 

 of early spring. We have seen that several gulli- 

 ble or foolhardy herbs may be cheated or dared 



