February 24, 1905.] 



SCIENCE. 



311 



were pointed to as proving this hypothesis. 

 The fatal objection to this theory is that en- 

 tirely identical mounds are found in Indian 

 Territory on flat plains underlaid by higher 

 inclined carboniferous shales and sandstones, 

 where the substructure clearly lacks the ele- 

 ments required by this hypothesis. 



The dune theory is based on the resemblance 

 of these mounds to the low dunes which col- 

 lect in the semi-arid region of the west about 

 clumps of low vegetation. The objection to 

 this theory is the great irregularity of wind- 

 made features and the very notable uniformity 

 in size and exact resemblance, one to another, 

 of these natural mounds of the south central 

 United States over an area at least 300 miles 

 wide and 500 miles long. It would seem that 

 in so large an area a wind origin would in- 

 volve a greater variation in size than has been 

 observed, and necessitate the presence of occa- 

 sional dunes, or lines of dunes, of noteworthy 

 size, whose origin could not, in any way, be 

 doubted. 



In the ant hill theory two possible lines of 

 development were suggested : (1) that the 

 mounds are the work of the atta, or leaf-cut- 

 ting ants, (2) that they are the remains of 

 hills of the mound-building variety of white 

 ants, the termites. Accoi'ding to Professor 

 W. M. Wheeler, atta hills in western Texas 

 reach a diameter of forty to fifty feet and 

 height of one to two feet; and Mr. E. A. 

 Schwarz, of the National Museum, reports 

 that the atta hills in Cuba often reach a 

 height of ten to twelve feet and a diameter 

 several times as great. These occurrences 

 add greatly to the possibility of an ant origin. 



Regarded as the work of mound-building 

 termites, which are now restricted to the trop- 

 ical regions, these mounds suggest a warmer 

 and moister climate. Modifications such as 

 those which permitted large elephants, camels 

 and animals of the sloth and armadillo fam- 

 ilies to live in this region would also have 

 permitted these, now similarly restricted 

 mound-building termites, to do the same; and 

 the causes which resulted in the extinction of 

 the larger animals would also, though at a 

 later date, have destroyed the mound-building 

 termites. 



Of the theories of origin yet suggested none 

 are entirely satisfactory, and the dune and 

 ant hill theories are the only ones well sup- 

 ported. If either of these hypotheses is cor- 

 rect the mounds are indications of important 

 climatic changes in very recent time. It was 

 suggested that the matter should be approached 

 by the careful excavation of a number of these 

 mounds at widely diiferent points in order to 

 fully determine the relation of the mounds to 

 the beds which underlie them and to the soil 

 surrounding them. 



The last paper of the evening was by Mr. 

 A. S. Hitchcock on 'The Twigs of Woody 

 Plants with Deciduous Tips.' Woody plants 

 in our latitude ordinarily form well defined 

 winter buds at the time of elongation of the 

 season's growth in late spring or early sum- 

 mer. Such growth is often referred to as 

 definite or determinate. In some plants such 

 as the willow the growth of the twigs con- 

 tinues during the season and is retarded and 

 finally stopped by the advent of winter. Some 

 plants have the habit of casting or sloughing 

 otf the terminal portion of the young twig at 

 a definite point much as a leaf is cast in 

 autumn. Such twigs present a scar at the 

 end and, instead of a teiTtiinal bud, as in 

 hickories or walnuts, the uppermost lateral 

 bud continues the growth of the stem. Ex- 

 amples of this method are the elms, basswood 

 and many other woody plants with two-ranked 

 leaves. The tip of the twig is usually cast 

 in the summer when the buds are formed. 

 The speaker called attention especially to the 

 twigs of the common sumac (Rhus glaira) 

 gathered in December which showed remark- 

 ably long terminal portions of the twigs still 

 attached but with the well-defined delimiting 

 layer separating the healthy ripened wood 

 from the dead terminal portion (five or six 

 inches) which would be cast off during the 

 winter. E. L. Morris, 



Recording Secretary. 



THE ONONDAGA ACADEMY OF SCIENCE. 



The Onondaga Academy of Science held 

 its January meeting in Lincoln Hall of the 

 high school building, at Syracuse, on the 

 evening of the twentieth. Dr. John M. Clarke 



