130 



A study of a meter quadrat in a typical field during the month 

 of May, 1915, gave the following result: 



Phlox tenuis 189 



Oenothera lineafolia 44 



Oenothera sinuata minima 13 



Krygia occidentalis 43 



Rumex hastatulus 41 



Linum multicaule 13 



Sahbatia campestris 30 



Lechia Driimmondii 31 



Drosera annua 52 



Hedeoma (not identified) 270 



Outside of the quadrat but associated with D. annua were the 

 following : 



Linaria canadensis Lepuropetalon spathulatum 



Lepidium. intermedium Polygala incarnata 



Castilleia indivisa Tithymalus leiococcus 



Asclepiodora viridis Jatropa stimtilosa 



Geranium carolinianum Opuntia grandijlora 



Legousia perfoliata Helianthemum rosmarinifolium 



Allium Nuitallii Tragia ramosa 



Verbena Halei Diodea teres 



Linum medium, Houstonia patens 



Oenothera serrulata Crusea allococca 



Talinum parviflorum Polypremum procumbens 



No attempt was made to identify the grasses and plants below 

 the spermatophytes growing in the quadrat. 



Summary. — Drosera annua is an annual, appearing about 

 February i. 



The soil is a fine sand with a small per cent of silt and clay. 

 Hence it dries rapidly. The nitrogen content is low. 



The water content of its habitat ranges from six to twenty-five 

 per cent during the life period of the plant. 



The minimum requisite of water in this particular soil, as 



shown by the death of the plants, is six per cent, while the 



optimum lies somewhere beyond this point. 



Agricultural and Mechanical College of Texas, 

 College Station, Texas 



