4 24 IOWA ACADEMY OF SCIENCE 



On this area the weeds have succeeded very well for one 

 year's work, and have made conditions much more comfortable 

 for themselves. They have bound at least the surface soil with 

 their roots, so that there is much less washing than there was 

 during the preceding season. The presence of algae and mosses, 

 and of a few specimens of Equisetum arvense, testify to im- 

 proved moisture conditions. Some of the plants first observed 

 (notably the survivors of the former cultivated state) have 

 disappeared: lack of time for careful botanizing has prevented 

 the preparation of a list of the missing. Most of the plants 

 still remain and thrive, however, and a few new arrivals may 

 be reported. Two of them. Salsola tragus and Lepidium vir- 

 ginicum, were probably rolled in as tumbleweeds from the rail- 

 road embankment against which one end of the levee abuts; 

 the remainder (listed below) were probably wind-sown. 



The main point of interest in this year's observation, how- 

 ever, is concerned with the changes of dynasty which are tak- 

 ing place in this little corner of the vegetable kingdom. In 

 the first paper the pigweed. Amarcmtliiis retroflexus, was re- 

 ported as the dominant plant. A prolific seeder, holding more- 

 over a goodly proportion of its offspring until well into the 

 following growing season before launching them on their colon- 

 izing ventures, it was well prepared to become master of the 

 situation presented by the newly bared soil exposed after spring 

 was well advanced. With it, as noted before, went the goose- 

 foot. Chenopodium album, which possesses some of the same 

 characteristics. A considerable sprinkling of this plant was in- 

 - >ersed with the dominant amaranth, but the amaranth re- 

 mained after all the king of the colony during the first season. 



But with the arrival of the second spring the situation was 

 radically changed. The Chenopodium proved to be an early 

 riser, and thus got the start of its cousin weed. During the 

 latter part of March the writer went over the ground, and the 

 principal sign of life on the levee was the presence of Chena- 

 podium seedlings all over the place. They were as ubiquitous 

 as the Amaranthus had been during the preceding season, and 

 in places formed dense sods. Xo seedlings of the pigweed were 

 as yet to be seen. Observations a couple of months later showed 

 the logical result. The dominant plant was now the Chenopo- 



