MARYLAND WEATHER SERVICE 171 



small area each year so that the woodman may complete the cir- 

 cuit of his forest in say ten years, and then cut again from the 

 area first cut over. Among the advantages of this plan is the smal- 

 ler damage done to seedlings by hauling the timber. Where Chest- 

 nut or the Tulip Tree are the important trees, the method of cop- 

 picing is desirable. The treatment of the Chestnut is the subject 

 of a recent bulletin of the Department of Agriculture.* 



MARSHES. 



The term "marsh" is here used to include those hydrophytic areas 

 where grasses or other herbaceous vegetation dominate, as do trees 

 in what have been called "swamps." Two well-marked associations 

 exist, depending on the salt content of the water, so that fresh and 

 salt marshes may be considered separately, though transition or 

 tension areas are easily to be found. 



Fresh Marshes. 



Fresh marshes occur along the shores of slow-running rivers and 

 of ponds which are provided with an outlet. In case the banks are 

 gently sloping, a well-marked zonation may be seen. Beginning 

 with the zone which occupies the deepest water, there may be dis- 

 tinguished : 



Potamogeton zone. — Several species of Potamogeton, especially 

 Potamogeton natans, inhabit water 5 to 10 feet deep, which may 

 flow with fair rapidity without destroying the plants. In quiet 

 water such as ponds the Potamogeton is frequently accompanied by 

 Brasenia purpurea and such free-swimming plants as Utricularia. 

 Lemna and Spirodela. Other plants do not invade this zone on ac- 

 count of their inability to bring the leaf-blades to the surface of the 

 water. This zone is often absent, owing, perhaps, to the too sudden 

 descent of the river-bottom. Occurring in similar situations, though 

 not with sufficient frequency to be listed separately, is Vallisneria 

 spiralis, which was observed in inlets from the Gunpowder River. 



•Bureau of Forestry, Bull. 53. 



