514 



SCIENCE 



[N. S. Vol. XXXI. No. 796 



the ¥. S. National Herbarium (Vol. 13, pt. 2) 

 illustrating the paper by five fine photographs. 



Professor Aven Nelson's " Contributions 

 from the Eoeky Mountain Herbarium," VIII. 

 (Bot. Gaz., XL VII.), includes many new 

 species from the deserts of southern Nevada 

 and adjacent Arizona, collected by L. N. Good- 

 ding in 1905. 



Dr. E. L. Greene has taken time enough 

 from his historical studies to bring out a 

 number of descriptive or critical papers, 

 among which are " New Californian Aster- 

 aceae," " Some Western Caulescent Violets," 

 " Two New Southern Violets," etc., in his 

 Leaflets of Botanical Observation and Criti- 

 cism (Vol. H.) ; and " Some Thalictra from 

 North Dakota " in the Midland Naturalist 

 (October, 1909). Three new species are de- 

 scribed. 



Professor W. L. Jepson's " Synopsis of the 

 North American Godetias " (University of 

 California Publications, Vol. 2, No. 16) is a 

 careful and exhaustive study of the species of 

 this Pacific coast genus. Seventeen species 

 are recognized, of which six are new. A help- 

 ful plate accompanies the paper. 



Another paper on cactuses — " Cactaceae of 

 Northeastern and Central Mexico," by W. E. 

 Safford (Smithsonian Report for 1908), adds 

 materially to our knowledge of these interest- 

 ing plants. The first twenty pages are de- 

 voted to a general discussion of the structure, 

 morphology and classification of the cactuses 

 at large, while the remaining eighteen pages 

 are given to a synopsis of Mexican Cactaceae. 

 Fifteen fine plates and twenty-four text figures 

 make this a valuable paper for any one who 

 wishes to learn about the Cactaceae. 



Here we may briefly mention Professor 

 SchafEner's " Pteridophytes of Ohio," which is 

 in reality an excellent local manual of these 

 plants ; Professor Shimek's " Flora of Winne- 

 shiek County" (Iowa), being a useful anno- 

 tated list, with ecological discussions; Pro- 

 fessor L. H. Harvey's " Floristic Composition 

 of the Vascular Flora of Mount Ktaadn, 

 Maine," with analytic tables and discussions; 

 and lastly Professor Euth Marshall's " Vege- 

 tation of Twin Island" giving the results of 



several summers' studies of a small island in 

 Lake Spooner in northwestern Wisconsin. 

 It contains a suggestion as to what may be 

 accomplished scientifically while having a 

 good outing. Charles E. Bessey 



The University op Nebraska 



SPECIAL ARTICLES 



' THE SEX-DETERMINING! CHROMOSOMES IN 

 ASCARIS 



In 1908 Professor Boveri observed in an 

 especially large number of the fertilized eggs 

 of Ascaris megalocephala iivalens, a small 

 chromatin element which he had already previ- 

 ously seen, and thinking that it might be a 

 sex chromosome, he suggested to Miss Boring 

 that she should make an exact study of the 

 chromatin conditions in this species. Though 

 Miss Boring obtained important results,' she 

 could not arrive at any positive conclusion 

 concerning the significance of this element. 

 In an appendix to Miss Boring's paper (I. c), 

 Professor Boveri concludes that this small 

 chromosome in Ascaris megalocephala is a sex- 

 determinant, and also reports the finding by 

 himself and Gulick, of a heterochromosome in 

 Heterahis, which behaves exactly like the 

 heterochromosome in some hemiptera (type 

 Protenor, of Wilson). 



Following the suggestion of Professor 

 Boveri, I have worked upon the spermato- 

 genesis of Ascaris megalocephala and Ascaris 

 lumhricoides. In the maturation divisions of 

 the spermatogenesis of Ascaris megalocephala, 

 which have been very accurately investigated 

 by O. Hertwig and Braur, and also by Miss 

 Boring, nothing has been observed hitherto of 

 an independent chromatin element that could 

 be interpreted as a heterochromosome. Boveri 

 (I. c.) has oifered as an explanation for this 

 condition, that the heterochromosome here 

 may be united with one of the large chromo- 

 somes. Studying a great number of males of 

 Ascaris megalocephala, I have found one in 

 which an independent heterochromosome can 

 be followed throughout the whole maturation 

 period and another in which it is present in 



* Archiv f. Zellforschung, V. 4. 



