I 



r 



ECOLOGICAL CROSS SECTION OF THE MISSISSIPPI- ISl 



cleared at various times during the year, harbor none but 

 species with perennial roots or those the seeds of which are 

 produced in great abundance. The spring flora, in addi- 

 tion to the two species just mentioned, is limited chiefly to 

 the Carices, and it is the summer which brings a compara- 

 tively large number of species, many of them water-loving. 

 Among them Laduca Scariola, L, Scariola integratay Lippia 

 lanceolatay Stachys palustris^ Oxyhaphiis nydagineus^ and 

 species of Polygonum^ are prominent. Where there is stand- 

 ing water one sometimes meets with Typha lati folia and 

 Lemna perpudlla. This summer aspect is not materially 

 changed during the autumn. 



The embankment. 



The railroad tracks themselves do not present conditions 

 favorable to plant growth and this is limited to occasional 

 rosettes of Capsella Bursa-pastonSj Lepidium virginicu7n, 

 Portulaca oleraceaj Taraxacum officinale^ Amaranihus retro- 

 flexiis and Mollugo verticillata , both the Amaranthus and the 

 Portulaca not appearing till the year is well advanced, while 

 the rosettes of Mollugo verticillata remain till the October 

 frosts kill them. 



The land on either side of the track harbors a large num- 

 ber of species. The stretch next to the hillside is occupied 

 mainly by many of the herbaceous plants which properly be- 

 long there while the opposite side bears numerous grasses or 

 a growth of Rhus glabra, which from time to time, and es- 

 pecially during the late summer, is cleared aw^ay, being cut 

 and subsequently burned over (plate 16). Among the 

 principal grasses, besides Poa pratensis, are Asprella Hystrix, 

 Bromus secalinus^ Dactylis glomerata and Phleum pratensCj 

 to which, during the summer, Eleusine indica^ Panicum 

 sanguinale ,P halaris canariensis, Setaria glauca, S. italica, 

 S. viridis and Triodia cuprea are added. Hypericum per- 

 foratum, Oenothera biennis^ Matricaria discoidea and Ver- 

 bascuni Thapsus, as well as Commelina communis and 

 C, virginica are typical here, as are the different species 

 of Plantago. Abidilon Avicennae, Rhus Toxicodendron, A- 

 chillea Millejolium, Laduca leucophaea integrif olia , L . Scariola 



