270 THE PLANT WORLD 



a total range in excess of the variation of conditions which 

 would be furnished by a vertical mile of mountain slopes. 

 Then a large number of other forms occur in very narrowly 

 restricted areas or pockets, evidently determined by local 

 drainage or moisture conditions, so that an analysis of their 

 inter-relations which would make possible a delimination of 

 "life zones" is extremely difficult. Thus, in traversing the 

 slopes from 4,000 feet in the vicinity of Tucson to sea-level, 

 the only place where any distinct alteration in the character 

 of the flora may be discerned is at the junction of the lava 

 beds with the gravelly detrital plains, and at the contact of 

 the sand dunes with the playas on one hand and with the 

 coastal formations toward the Gulf. 



PECULIARITIES IN THE KNOWN DISTRIBU- 

 TION OF SOME SPECIES OF CEDAR APPLE. 



By R. E. Stone. 



In giving the geographical distribution of any particu- 

 lar species we can take into account only those points at 

 which the species has actually been collected. Of course if 

 two collections have been made at no great distance from 

 each other, the probability is that the species will be found 

 between these two points provided physical conditions are 

 uniform. But if the collections were made at widely sepa- 

 rated points, the question as to whether the species exists 

 between those points could only be demonstrated by making 

 a careful search for it. 



It is a question of the latter sort that prompts me to 

 present this article. The white cedar, Chamaccyperus 

 thiiyoides, is affected by two kinds of cedar rust somewhat 

 resembling the cedar apple found on the red cedar, Sahina 

 virginica. One of these, Gymnosporangium ellisii, produces 

 spindle-shaped swellings on the branches of the white cedar. 

 The spore masses protrude through the bark of the affected 

 portion in the from of light yellow or whitish projections 



