MARYLAND WEATHER SERVICE L4 1 



tidal currents, which they are structurally well fitted to withstand. 

 In more protected situations Myriophyllum humile, Potamogeton 

 pectinatus and Naias flexilis occur, while in the quite shoal waters 

 Hetercmthera rcniformis, Eriocaulon septangulare , Isnardia palus- 

 tris and Utricularia gibba form the first zone of plants outside the 

 emersed aquatics. 



There is no part of the Eastern Shore in which there is a larger 

 number of constantly flowing streams of small size than in Dor- 

 chester County, where the various feeders of the Blackwater, Trans- 

 quaking and Chicacomico rivers possess a greater variety of aquatic 

 vegetation than is found elsewhere. Various species of Potamogeton 

 are the commonest and most conspicuous of these, including Pota- 

 mogeton natans, Potamogeton nuttallii, Potamogeton, pulchcr, 

 Potamogeton lonchites, and Potamogeton diversifolius, together 

 with Ceratophyllum demersum, Myriophyllum pinnatum and 

 Utricularia gibba. Quieter waters abound in Costal ia odorata, 

 Brasenia purpurea and Limnantliemum aquaticum, mingling often- 

 times with such plants as Nymphaea advena, Pontederia cordata, 

 Peltandra virginica, Polygonum amphibium and Rumex verticil 

 latuSj which border the marginal Stream Swamps. The only float- 

 ing members of the aquatic flora, Lemna minor and Spirodela 

 polyrrhiza, are abundant in the quiet margins of such streams, often 

 accompanied by the Hepatic Riccia fluitans. In both quiet and 

 swift-flowing waters Callitriche heterophylla is abundant, together 

 with Potamogeton diversifolius. (See Plate VI, Fig. 1.) 



The still waters of the artificial mill-ponds so abundant on the 

 Eastern Shore are not essentially different in their aquatic flora 

 from the streams just described. Castalia, Brasenia, and such spe- 

 cies as Utricularia vulgaris, Potamogeton nuttallii and Potamogeton 

 natans, Naias flexilis and Myriophyllum humile are wide-spread and 

 abundant. By no means wide-spread and found only in standing 

 water is the interesting Utricularia inflata, which is conspicuous on 

 the surface of the water by reason of the five to eight radiating stems 

 which are enlarged by spongy tissue in a manner which enables them 

 to serve as organs of flotation. 



