258 



SCIENCE 



[N. S. Vol. XXXIX. No. 998 



vigorous plants from 6 to 12 inches tall. Plants 

 thus treated were held in a moist atmosphere at 

 20° to 25° C. over night and removed the follow- 

 ing morning. 



It is believed that by this method it is pos- 

 sible to learn the relative resistance of any va- 

 riety without growing it under field conditions. 



Plus and Minus Strains in the Genus Glomerella: 



C. W. Edgeeton. 



Cultures of Glomerella from different hosts have 

 been obtained which show the presence of two 

 different strains, these being provisionally called 

 plus and minus strains. The plus strain pro- 

 duces normal perithecia in clumps or masses. 

 The minus strain produces perithecia, usually im- 

 mature, scattered profusely over the surface of 

 the culture medium. When these two strains are 

 placed in the same plate and allowed to grow 

 together, a dense black ridge of normal peri- 

 thecia develops on the boundary line. The two 

 strains of one of these fungi have been carried 

 for over three years and are still producing peri- 

 thecia abundantly. That there is a fertilization 

 between the two strains has been proven by iso- 

 lating single asci from the boundary line be- 

 tween the two strains and allowing them to grow 

 into colonies. These colonies usually produce both 

 strains. 



The Homology Between Spore-forms in the 



Ascomycetes: C. E. Orton. 



It has been pointed out in the rusts that there 

 is a very striking morphological similarity be- 

 tween certain heter(Ecious species. This morpho- 

 logical likeness may be termed homology. It is 

 pointed out in this paper that a similar homol- 

 ogy exists between the conidial and aseigerous 

 stages of certain Ascomycetes with respect to 

 morphology of their spores. Examples are cited 

 and discussed which show the likeness as well as 

 the apparent exceptions. It is hoped that this 

 fact may be of value to the mycologist and plant 

 pathologist as a guide to life-history studies. 



A Contribution to the Life History and Physiol- 

 ogy of Cylindrosporium on Stone Fruits: B. B. 



HiGGINS. 



A careful study of the life history of this para- 

 site has brought to light a very interesting poly- 

 morphism. Eour spore forms were found to be 

 genetically connected in the life cycle as follows: 

 Typical Cylindrosporium conidia, produced on 

 delicate stromata in spring and summer; mi- 

 croeonidia, produced on the same stromata in late 

 fall; ascospores, produced in apothecia in the 



dead leaves during the following spring; and 

 apothecia! conidia, produced later in the same 

 apothecia following the discharge of the asco- 

 spores. All of these except the microconidia are 

 capable of producing infection on the host plants. 



A study of the morphological and biological 

 characters of the organism from eight species of 

 Prunus showed that the forms under considera- 

 tion fall naturally into three species, one on each 

 of three more or less distinct divisions of the host 

 genus. 

 North American Species of Feridermium on 



Pine: J. C. Arthtje and F. D. Kern. 



The authors published a paper covering this 

 ground in 1896, since which time much informa- 

 tion has been added to previous knowledge, which 

 the authors now propose to summarize. Some of 

 the former names have been reduced to synonymy, 

 chiefly as the result of culture work, and two 

 new species are established, one from California 

 and one from Guatemala. Some three or four 

 species have been introduced from Europe, and 

 are yet local. Doubtless the greatest economic in- 

 terest centers about the caulicolous forms, native 

 and foreign, and these have been discussed with 

 considerable fulness. 

 Transpiration of Silphium laciniatum L. : L. A. 



GiDDINGS. 



The experiments discussed in the present paper 

 were carried on with Silphium laciniatum L. 

 This plant was selected for experimental pur- 

 poses because of the fact that it is a xerophyte 

 growing in very dry exposed prairie regions and 

 because, being taller than most of our native 

 prairie plants, it offers opportunities for the 

 study of normal transpiration in relation to evap- 

 oration at different altitudes above the surface of 

 the soil. 



The paper includes a discussion of the experi- 

 ments carried on in the laboratory and in the 

 field. A part of the experiments were carried on 

 in the plant physiology laboratory of the State 

 University of Iowa. The field experiments were 

 carried on at the Macbride Lakeside Laboratory 

 on West Lake Okoboji dnring the summer of 

 1912. Material for the study of the structure of 

 the leaf was collected at the same time that the 

 field experiments were being performed. 



In the laboratory special attention was given 

 to the effect of increased wind velocity on the 

 rate of transpiration. Evaporation experiments 

 were run with the transpiration experiments for 

 comparison. In the field experiments attention 

 was also given to the effect of wind velocity on 



