MARYLAND WEATHER SERVICE L93 



chrus tribuloides, Monarda punctata and Lespedeza sp. If a field 

 lies fallow for a longer time, say, three or four years, woody plants 

 become evident, for example, trailing vines such as Rubus cana- 

 densis, *Lonicera japonica, Tecoma radicans and Smilax sp.. shrubs 

 such as Rubus villosus and lllius copallina, trees such as Piiuis 

 virgmiana or Pinus taeda. Robinia pseudacacia and Diospyros vir- 

 giniana. Just what trees make their appearance depends largely on 

 the species found in the immediate vicinity. As in the case of her- 

 baceous plants, invasion is most rapid in the case of those species 

 whose seeds are easily carried by the wind. 



Burned areas may be briefly considered as a supplement to the 

 foregoing. The first plants which appear are necessarily of xero- 

 phytic habit, since the humus of the soil is generally destroyed by 

 the fire, and danger from exposure to strong insolation, etc., is great. 

 Readiness ' of distribution by wind also is a determining factor. 

 Among the pioneers are: Diodia teres. Ambrosia artemisiaefolia, 

 Chamaenerion angustifolium (fireweed), Cassia nictitans, *Lespe- 

 deza striata, Coreopsis verticillata. Another class sure to be repre- 

 sented in the year following devastation includes plants whose sub- 

 terranean parts escape destruction: Pteris aquilina, *Rumex ace- 

 tosella, Baptisia tinctoria, Lupinus perennis, Sericocarpus asteroides. 

 Shruhs are almost sure to make their appearance in a few years, as 

 for example, Vaccinium sp., Pieris mariana, Clethra alni folia and 

 Azalea nudiflora. The arboreal vegetation sometimes escapes with 

 slight damage, so that pines and oaks are frequently found standing. 

 Young growth of the same species may spring up, but the Scrub 

 Oak and Black Jack are apt to appear also. Fortunately forest 

 (ires are of rare occurrence in the region, so that only a few areas 

 were found for the study of this topic. Hence the results are frag- 

 mentary. 



RELATION OF VEGETATION TO SOIL. 



The belief is widespread that the fertility of a soil may be judged 

 from an inspection of the natural vegetation growing upon it. That 

 the method is of limited application is seen from the fact that in 

 Southern Maryland a tract covered with pine indicates in general 



