646 



SCIENCE 



[Vol. LV, No. 1433 



This renders it possible to. deal with the trian- 

 gulation of all three of these countries in one 

 grand computation, — a possibility not equalled 

 anjTvhere else in the world at present. 



More than 15,000 miles of precise leveling 

 has been done in the United States in the past 

 decade, all of the highest standard of accu- 

 racy. The total for the United States previous 

 to 1912 was 30,000 miles, of which a part was 

 of a lower grade of accuracy than the recent 

 work. This leveling is primarily for engineer- 

 ing purposes for the control of surveys upon 

 which good maps depend. But in due time the 

 reviewer believes it will be found of much 

 value to science as a means of measurement of 

 the slow geological changes in the relative ele- 

 vation of different parts of the earth's surface. 

 Such changes may be detected at the coasts by 

 direct reference to the mean surface of the sea. 

 In the interior of a continent the precise level- 

 ing, repeated for this purpose, will furnish the 

 only means for determining changes in relative 

 elevation comparable in accuracy with the shore 

 studies just referred to. 



Among the more important improvements in 

 apparatus made in the past ten years may be 

 mentioned : ( 1 ) improvements in the precise 

 leveling instrument, which many years of use 

 had already shown to be the best instrument for 

 its purpose in the world; (2) improvements in 

 the precise level rods; and (3) improvements 

 in the half-second pendulum apparatus and its 

 auxiliaries intended to enable one to make the 

 oljsei'vations more rapidly and economically 

 without any reduction of accuracy. 



The brief statements which have been made 

 show the character of the information given 

 in the report, and some of the reasons why all 

 who are interested in geodesy should have a 

 copy. The report contains numerous especially 

 well prepared maps showing the places at 

 which each of the various classes of observa- 

 tions — astronomic observations, triangulation, 

 gravity determinations, precise leveling — have 

 been made. It also contains the best available 

 summary, in several separate topical lists, of 

 the bibliography of geodesy and closely related 

 subjects in the United States in the past decade. 



John F. Haypord 



SPECIAL ARTICLES 



.A HAPLOID MUTANT IN THE JIMSON WEED, 

 "DATURA STRAMONIUM" 

 The normal Jimson Weed is diploid (2n) 

 with a total of 24 chromosomes in somatic cells. 

 In previous papers^ the finding of tetraploids 

 (4n) with 48 chromosomes and triploids (3n) 

 with 36 was reported, as well as unbalanced 

 mutants with 25 chromosomes represented by 

 the formula (2n -|- 1). The finding of two 

 haploid or In plants, which we are now able to 

 report, adds a new chromosomal type to the 

 balanced series of mutants in Datura. This 

 series now stands: In, 2n, 3n, 4n. Since a 

 series of unbalanced mutants has been obtained 

 from each of the other balanced types by the 

 addition or subtraction of one or more chromo- 

 somes, it is possible that a similar series of 

 unbalanced mutants may be obtainable from 

 our new haploid plants, despite the great un- 

 balance which would thereby result. 



The haploid individuals were two from a 

 number of plants of abnormal appearance 

 secured in an attempt to induce chromosomal 

 irregularities by the application of cold as a 

 stimulus. The large amount of bad pollen con- 

 sistently found in its flowers — 80 per cent, and 

 more empty grains have been counted— indi- 

 cated, even before chromosome counts were 

 made, that we were not dealing with a mutant 

 of a previously known type. A detailed study 

 of the assortment of chromosomes and of the 

 possible breeding behavior is being undertaken. 

 The cytological data so far as obtained, how- 

 ever, may be briefly summarized. 



The late prophase, or metaphase, of the first 

 division in pollen-mother-cells shows 12 un- 

 paired chromosomes only. The cortex of the 

 lateral roots also shows 12 chromosomes. 



The 12 chromosomes in the poUen-mother- 

 eell undergo a "reduction" into 3+ 9, 4+ 8, 

 etc. These reduced groups divide in the second 

 division forming usually 4 nuclei and subse- 

 quently 4 cells. The resulting young pollen 

 grains with less than 12 chromosomes appar- 

 ently all abort. 



1 Science, 1920, N. S. 52: 388-390; Amer. Nat., 

 1921, 55; 254-267; Amer. Nat., 1922, 56: 16-31. 



