Maech 17, 1899.] 



SCIENCE. 



413 



Archean of the Lake of the Woods forms a 

 series of troughs — four is the number given — 

 in which the Keewatin schists now lie. [Com- 

 pare Geol. and Nat. Hist. Sur., Canada, N. 

 Ser., Vol. I., 1885, C. C, pp. 10 et seq.] Al- 

 though there are no sharp unconformities to be 

 seen, yet, as Lawson observes, "the fact that 

 we find in the Keewatin series the first un- 

 doubted evidences for this region of aqueous 

 sedimentation and also of volcanic action, while 

 in the underlying Laurentiau gneiss of the re- 

 gion we find evidence of neither, more than 

 suggests that the Keewatin series had a totally 

 different kind of origin from that of the 

 gneisses and must, therefore, be in unconform- 

 able relation to them " [Ibid., p. 84]. 



At Rainy Lake H. V. Winchell and Grant 

 found a series of granites and granite gneisses 

 beneath the other rocks (r. e., Archean) and 

 eruptive into them. Since these authors did 

 not think best to distinguish between under- 

 lying and eruptive granite rocks their work 

 is of but little taxonomic value. [Geol. and 

 Nat. Hist. Surv., Minn., 23d An. Rep., 1895, 

 p. 53.] 



Between Rainy Lake and Lake Superior there 

 are several belts of schists with alternating 

 granites and other rocks having a general 

 northeast- and-south west trend. Concerning 

 one of these, Irving noted in 1886 "that we 

 have among the rocks * * * two types, in one 

 of which the crystalline structure is com- 

 plete and in which there is little or none of an 

 original fragmental structure, while in the other 

 the fragmental texture is still distinct and the 

 alteration has progressed to a smaller degree." 

 He then adds " that the supposed older one of 

 the two groups of schists in the Vermilion Lake 

 belt is intricately penetrated by the granites of 

 the great areas north and south of the belt." 

 [7th An. Rep. Director U. S. Geol. Sur., 1885- 

 86, p. 437.] Hence areas of Archean lie north 

 and south of these older schists. 



In the Minnesota River Valley lies the most 

 carefully studied series of granite gneisses, 

 gneisses and gabbro schists of the State. These 

 rocks occur quite continuously from New Ulm 

 to Ortonville and beneath the glacial drift 

 stretch westward into South Dakota and disap- 

 pear beneath the Dakota sandstone. At New 



Ulm they clearly underlie a quartzite conglom- 

 erate regarded as Huronian (whether lower or 

 upper is not determined). This Archean series 

 is divided, for purposes of study, into a lower 

 and upper ; the former is named the Ortonville 

 group of augite, hornblende and biotite granite- 

 gneisses, and the latter the Granite Falls group 

 of hornblende and biotite gneisses and asso- 

 ciated gabbro schists. [Hall, Syllabus of Geol- 

 ogy, 1897, p. 83.] 



F. W. Saedeson, 



Secretary. 



THE BOTANICAL CLUB OF THE UNIVERSITY OF 

 CHICAGO. 



At a recent meeting of the Club, Dr. Otis W. 

 Caldwell gave the results of his study of Lemna 

 minor. The following is an abstract of his 

 paper : Owing to the greatly reduced body of 

 the sporophyte of the Lemnacese there has been 

 much interest in its morphology, and in the 

 question as to the effect of the reduction upon 

 the gametophyte. The investigations show 

 that the sporophyte body is neither stem nor 

 leaf, as often contended, but a shoot undiffer- 

 entiated except at the basal or foot region and 

 at the nodal region from which the root, the 

 new shoots and the flowers arise. The root 

 originates from a small group of hypodermal 

 cells on the lower side of the node. The epi- 

 dermis develops a temporary root sheath, while 

 the persistent root cap is developed from the 

 meristem, which is never many-celled and in a 

 few cases was seen to be unicellular. Flowers 

 are rarely formed, and frequently when they 

 have begun to develop they are crowded out by 

 vegetative buds which are produced in great 

 abundance. Even when not encroached upon 

 by vegetative shoots the flowers do not often 

 succeed in forming seeds. The pollen grains 

 usually become fully formed, but the structures 

 of the ovule and embryo-sac may disorganize at 

 any stage in their growth. Although the chief 

 stages in ordinary embryo-sac development 

 were found, such were shown by very few 

 preparations ; while in most of the preparations 

 embryo-sacs were disorganizing, the disorgani- 

 zation first affecting the antipodals, then the 

 polar nuclei or primary endosperm nucleus, the 

 egg being the last to succumb to the unfavor- 



