POPULAR MISCELLANY 



123 



western Iowa, offers a very ingenious the- 

 ory, and one that certainly appears to ac- 

 count for the phenomena observed by him 

 in the above-mentioned region. He finds 

 that 1. In the hill-regions where the slopes 

 are inclined from 5 to 10, timber occurs 

 mostly on the northern slopes, just south 

 of creeks flowing east or west ; it occurs a 

 little less frequently on western slopes, east 

 of creeks flowing north or south ; 2. In the 

 bluff-region, where the slopes are from 10 

 to 45, just east of the bottom-lands of the 

 Missouri, timber is found over most of the 

 surface. This belt of timber-land is usually 

 bounded on the west by the crest of the 

 most western ridge of the bluffs, leaving 

 the slopes facing the bottom-land bare, ex- 

 cept when a lake, slough, or stream, comes 

 close to the base of the bluffs, or where the 

 bluff-side is deeply furrowed by ravines; 3. 

 In the low alluvial valleys, timber is found 

 along the streams, usually in narrow strips, 

 and generally wider on the east and north 

 banks ; the rest of the bottom-land is desti- 

 tute of trees and bushes. According to the 

 author, constancy of moisture is the condi- 

 tion sine qua non of forest-growth ; and, 1. 

 This constancy of moisture must be in one 

 or both the media in which the trees are 

 to exist the soil or the air ; 2. It is plain 

 that moisture of soil will be more constant 

 on northern slopes than southern, the former 

 being less exposed to the sun's heat. In 

 the spring, and after showers, the northern 

 slopes dry up more slowly, and, at certain 

 degrees of humidity of the air, the moisture 

 given off by the southern slope of a hill may 

 be condensed by the northern. These and 

 other like considerations may perhaps ac- 

 count for the timber occurring on northern 

 slopes, while it is nearly absent from south- 

 ern ; 3. The fact that the prevailing winds 

 of Southwestern Iowa in spring and summer 

 are westerly may perhaps explain the pre- 

 ponderance of timber -areas on the east 

 banks of the streams flowing south ; and 

 this, combined with the increased roughness 

 of the surface, may also go far toward ex- 

 plaining the timber-belt of the bluff-region ; 

 4. It remains to explain the distribution of 

 timber and prairie in the alluvial valleys. 

 Here layers of clay prevent the ready drain- 

 age of many parts ; these conditions render 

 much of the surface too wet (for trees) at 



all times, while other places are too wet in 

 spring and too dry in summer. On the 

 other hand, the occurrence of trees along 

 the streams and on ridges along old chan- 

 nels may be explained partly by the in- 

 equality of surface, making the drainage 

 of surplus water possible, so that moisture 

 around the roots is more constant than else- 

 where on the bottoms. 



More about the Agricultural Ant. While 

 visiting Texas last summer, the Rev. H. C. 

 McCook attentively studied the habits of 

 the agricultural ant {Myrmica molefaciens). 

 His observations are, for the most part, 

 strongly confirmatory of the statements 

 made by the late Dr. Lincecum ; but he also 

 adds to our knowledge of these interesting 

 insects a number of new and interesting 

 facts. Mr. McCook has published, in the 

 " Proceedings of the Academy of Natural 

 Sciences of Philadelphia," a general prelimi- 

 nary statement of his results, intending soon 

 to treat the subject more fully. He carried 

 on his observations in the vicinity of the 

 city of Austin, where the soil is black and 

 sticky, varying in depth from three feet to 

 a few inches. The formicaries of the agri- 

 cultural ants are commonly flat, circular 

 clearings, hard and measurably smooth, 

 aptly called "pavements" by Lincecum. 

 A few of them had in the centre low 

 mounds, a few inches in height, and two or 

 three in diameter. The formicaries vary 

 in width from twelve feet to two or three 

 feet. They are invariably located in open 

 sunlight. The process of making a clear- 

 ing strongly suggested the modes of pio- 

 neers in a forest spires of grass taking the 

 place of trees. The chain of evidence that 

 determines these ants to be true harvesters 

 in as follows : 1. Workers were seen gather- 

 ing seeds and carrying them into the formi- 

 caries through the central gates ; 2. The 

 same seeds were found in granaries within 

 the opened formicaries ; 3. The seeds, with 

 outer shell removed, were found in other 

 granaries ; 4. The ants were found carrying 

 out shells to the refuse-heaps. The author's 

 opinion is, that these ants do not plant 

 seeds on purpose, but that they carefully 

 preserve on the outer margin of the clean 

 space the growths which arise from seeds 

 dropped accidentally. To the question 



