80 I. M. JOHNSTON 



Pinus ponderosa Dougl. var. Jeffreyi (Murray) Vasey. Common in the Upper 

 Transition Zone. 



It has often been pointed out that this variety and the species are at times 

 difficult to separate, a condition found to be very true in the San Antonio 

 Mountains. We always found trees at about the middle of the Transition 

 Zone which defied all attempts at placing them, despite the fact that we used 

 all the characters of bark, cones, foliage and seeds. The characters given to 

 the variety and those given to the species were found to be manifested in a 

 bewildering series of combinations which made the definite placing of these 

 trees an absolute impossibility. While we admit that the yellow pine found 

 on the ridges in the Upper Transition Zone is a fair variety of the yellow pine 

 which grows in the canons in the Lower Transition, we are inclined to think, 

 that in the light of the complete gradation of the one into the other, that 

 perhaps the rank of "form" would better indicate the true ^lationship of 

 the Upper Transition plant to typical P. ponderosa, at least in Southern 

 California. 



Pseudotsuga macrocarpa (Torr.) Mayr. Frequent in the Upper Chaparral Belt 

 and Lower Transition Zone. It grows as low as the mouth of San Antonio 

 Cafion, alt. 2000 ft. and as high as 7000 ft. alt. in Icehouse Canon. 



Abies concolor Lindl. & Gord. Common in the Upper Transition Zone, where it 

 is the dominant tree. 



CUPRESSACEvE 



Libocedrus decurrens Torr. General throughout the Transition Zone but not very 

 common. In the lower part of the zone it is found wholly in moist canons 

 or on streams banks, but in the upper part it is often found growing on talus 

 slopes or rocky mountain sides with fir and pine. Occasional trees are found 

 in moist situations in the chaparral belt descending as low as 2700 ft. alt. 

 (No. 1624.) 



Juniperus occidentalis Hook. One of the less common trees. In our mountains 

 the tree grows only in the Upper Transition Zone. The scattered colonies 

 have been found between 8000 ft. (Old Gold Ridge Mine) and 9660 ft. alt. 

 (Pine Mt. Summit). (Nos. 1400, 1623.) 



GNETACE.E 



Ephedra viridis Coville. A large colony on a dry, sunny hillside, alt. 5000 ft., in 

 Prairie Fork San Gabriel River. This station is on the lower edge of the 

 Transition Zone. Frequent on the desert base of the mountains. (No. 1721.) 



GRAMINE.E Si 



Stipa occidentalis Thurb. Not uncommon in bare rocky slopes in the Upper 

 Transition and Canadian Zones. (Nos. 1504, 1537.) 



Stipa Parishii Vasey. Throughout the Transition Zone, chiefly on gravelly 

 cafion floors. Apparently most abundant on the north side of the moun- 

 tains. (No. 1515.) 



