930 



SCIENCE 



[N. S. Vol. XXVII. No. 702 



The crystal is mounted so that the intersec- 

 tion edges of the faces to be measured are 

 parallel to and almost in line with the axis. 

 The goniometer is held so that the crystal is 

 close up to the eye, that is, with the protractor 

 part extending perpendicularly in front of and 

 away from one. The crystal is rotated by 

 means of the axis until the reflected image 

 of a window bar, electiic light or similar 

 object for a particular face coincides with 



'ffS 



some line of reference such as a chalk mark on 

 the floor, a ruler or the edge of a table. The 

 reading is taken for this face, then the crystal 

 is rotated until a similar image is obtained for 

 an adjacent face. The difference between the 

 two readings is the desired interfacial angle 

 (supplement angle). And so on for other 

 faces in the zone. As the protractor is a 

 semi-circle, only 180° of a zone may be meas- 

 ured at one time and the crystal must be 

 remounted for the rest of the zone. A face 

 must' always be connected up with its image. 



The sources of error are: first, the edge can 

 not be made to coincide exactly with the axis, 

 and second, the angles can not be read much 

 closer than quarter degrees. Yet the goni- 

 ometer furnishes a simple method of meas- 

 uring small crystals with bright faces even 

 when the faces are minute, and of testing 

 whether a given face lies in a given zone. 



Some measurements obtained on pyrite 

 crystals will show the accuracy of the instru- 

 ment. The calculated angles are indicated 



in parentheses alongside the measured angles. 

 210 A 311 = 25° (25° 14') ; 311 A 211 = 

 10° (10° 2') ; 211 A 111 = 20° (19° 28') ; 

 210 A 100 = 27° (26° 34') ; 210 A HI == 

 38° (39° 14'). These faces were all bright 

 and gave good images, but some of them were 

 less than one half mm. in width. 



Austin F. Eogers 

 Stantobd Univebsitt, Cal. 



the existence of rcestelia penicillata and 

 its telial phase in north america 



In taking up the study of the flora or fauna 

 of a new region systematists attempt to make 

 use of established names. In doing so they 

 sometimes apply them to forms afterwards 

 found to be wholly unlike those for which the 

 name was originally intended. The name 

 then occurs in the literature and the matter 

 of determining what the species listed under 

 it really are may require much subsequent 

 study. Such is the case, in the mycological 

 literature of North America, with Bcestelia 

 penicillata^ a very old European name dating 

 back to the time of the earliest mycological 

 workers. It was chiefly applied by the first 

 American authors attempting systematic work 

 in this field to the form Bastelia pyrata, 

 now known to be distinctly American, but 

 some other entirely distinct forms such as 

 Bcestelia glohosa and Bcestelia lacerata were 

 often referred to it, so that it is not possible 

 to determine in every instance just what spe- 

 cies some earlier American writers had in 

 mind when they used the name B. penicillata. 

 It was frequently used in local catalogues and 

 was much overworked, until somewhat later 

 it was authentically shown by an American 

 investigator^ that the genuine B. penicillata 

 of Europe was a very characteristic form dif- 

 fering materially from anything then known 

 in this country. At that time, however, ex- 

 ploration had not extended beyond the eastern 

 and central states, and that there should occur 

 in the western mountains strange and different 

 forms is not a matter of surprise, but that 



^ Rcestelia penicillata (Pers. ) Fries, Sum. Veg. 

 Scand., 2: 510. 1849. {JEcidiuni penicillatum 

 Pers.; Gmel. Syst. Nat., 2: 1472. 1791.) 



^Thaxter, Proc. Am. Acad., 22: 265. 1886. 



