152 Forest Club Annual 



Inner bark. The bast fibers are regularly arranged in 

 concentric layers. In Magnolia they are mixed with stone 

 cells. The bast parenchyma does not become sclerotic in Lirio- 

 dendron while in Magnolia it does,but only in the outer layers. 

 Stone cells in Magnolia are essentially enlarged and very thick 

 walled. The bast fibers in Magnolia have a typical form 

 while in Liriodendron they are often tangentially flattened. 

 Calcium oxalate is wanting in Magnolia and occurs in Lirio- 

 dendron as sand. Magnolia is characterized by secretion cells 

 which are developed from single parenchyma cells. Pith rays 

 are usually not more than three rows wide, but become broader 

 as they approach the middle bark. Their cells are more deli- 

 cately walled than the bast parenchyma and are generally 

 radially stretched. 



Key to Genera: 



Bast fibers arranged in regular concentric layers. 



1. The layers are a mixture of bast fibers and stone cells. 



In the young bast of the bundle the stone cells are 

 branched. The sieve tubes are very wide. (In the 

 inner bast layers stone cells are wanting). 



Magnolia 



2. The layers contain bast only; stone cells are wanting. 



The inner periderm is made up of alternate layers of 

 thin and thick walled cells. 



Liriodendron 

 Tilia. 



Outer bark. The phellogen has its origin in the layer of 

 cells immediately adjoining the epidermis. The superficial 

 periderm is fully developed at the end of the first vegetative 

 period; it is thick-walled and like the inner periderm in struc- 

 ture. The collenchyma is small celled. 



Middle bark. Typical collenchyma forms the outer layer. 

 The pelloderm is always found in Tilia. The slight tendency 

 to form sclerotic cells is characteristic. Calcium oxalate is 

 found in large quantities in the form of crystal aggregates. 



Inner bark. Bast bands are many cells broad and irreg- 

 ular in width due to a bunching of the fibers in places. The 

 bast fibers are always very long, straight and elastic, and are 

 thickened not less than one-third their width. No crystals are 

 present. The crystal cells contain peculiar large prisms, and 



