Aug. 7, 1916 Vegetative Succession Under Irrigation 751 



and other herbs, and the Hordeum phase, /. balticus, Rumex mexicanus, 

 Grindelia subalpina, and others mentioned. However, this does not 

 mean that D. caespitosa, for instance, would be absent from the latter 

 phase, but merely that it would occur more frequently in the former; 

 and so with /. balticus, which would be less abundant, though not neces- 

 sarily lacking, in the Agropyron association, and so on. 



Before the end of the second growing season seeds of the following 

 meadow plants will have germinated and taken root in the upland, so 

 that by the middle of the next (the third) summer, they will have become 

 a factor to be reckoned with. Therefore their consideration at this time 

 is not out of place. 



MEADOW PLANTS APPEARING ON UPLAND THIRD SEASON IRRIGATED 



Carex nebraskensis Dewey. 

 Carex Gayana Desv. 

 Carex lanuginosa Michx. 



Carex marcida Boott. 

 Gratiola virginiana L. 

 Agoseris glauca (Pursh) Steud. 



Carex nebraskensis is one of the commonest and most valuable * of 

 our sedges. It grows in clumps and reaches a good height. It is very 

 similar to C. variabilis, which is perhaps even more frequent. 



Carex Gayana is often the principal species of a given area. It is much 

 less robust than the other sedges and does not grow as tall. Another 

 drawback is that it has a tendency to mature early and turn yellow, losing 

 much in substance before harvest. C. lanuginosa, next to C. nebraskensis, 

 is probably the most important of the sedges. It is highly nutritious, 1 

 and its long narrow leaves and slender stems make it quite grasslike. 



The remaining species are mainly of interest because of their com- 

 paratively early appearance. They belong to that large series of meadow 

 plants which are present here, absent there, and are usually late in 

 coming in. A large proportion of the swamp species belong to this type 

 (P- 753)- By the end of the second summer, then, there has been a 

 considerable invasion of meadow plants. 



Plate CHI, figure 2, clearly shows what happens during the third season. 

 The reader will recall the presence of rush in the second-year condition 

 of the Agropyron association. Here it is rapidly replacing the wheat- 

 grass (stunted by too much water) and in the fall this phase were better 

 called the Juncus-Carex, or rush-sedge phase. The next summer (the 

 fourth) it will ordinarily reach its highest development. "Ordinarily," 

 because this step in the program is no doubt dependent on the resumption 

 of the usual controlled flooding, a method which, it will be remembered, 

 was temporarily forsaken because of insufficient water. During my 

 observation this resumption always took place, because by this time the 

 upland had reached the stage where a hay crop was assured and good 

 treatment justifiable. Owing to the relatively dry conditions, /. longi- 



1 Knight, H. G. t Hepner, F. E.. and Nelson, Aven. Op. cit. 



