88 THE PLANT WORLD. 



feet, a height of about thirty feet and greater age, it presents a 

 full, thickly clad and often beautifully rounded crown, but only 

 at the lower altitudes. 



As one approaches the mountains from the plains 6,000 feet 

 below, he finds the first tree, cropping up here and there, to be 

 the one-seed juniper. This increases in size, but gradually loses 

 its hold as the dominant species and at about 6,500 feet it dis- 

 appears. The alligator juniper first appears approximately at the 

 line of best development of the one-seed, and becomes dominant 

 where the latter ceases. On the succeeding steep slopes it is inter- 

 rupted by horizontal belts of shrubby blue oak. only to re-appear 

 as occasional lesser belts to the top of the higher slopes at 7,500 

 feet, and as extensive orchards on the malpais* mesas. It occu- 

 pies a large part of these tablelands at 7,000 feet, to the exclusion 

 of every other noticeable plant except grama and agave. Here, 

 however, our desert alligator becomes as picturesquely deformed 

 as its brother species below. Many trees show less than half their 

 girth covered with new wood bark. This gives rise to great 

 eccentricity of both trunk and limb. 



It will perhaps interest physiologists that on such limbs the 

 growth is always made on the lower side. The writer measured 

 one that was five inches in horizontal diameter at the crotch, grad- 

 ually widening to eight inches downward, with a vertical diameter 

 of twenty-eight inches. The pith of the limb was probably not 

 over two inches from the crotch. 



The dead parts, barring fires, persist for many years owing to 

 the absence of the fungi of decay. The living tree undoubtedly 

 exists to a great age as well. The age of both species is difficult 

 to ascertain. This is due to the formation of two annual rings 

 per year — thus more properly called " semi-annual rings " — 

 Ijrought on by two distinct growing seasons. The winter rain and 

 snow give rise to the first growth early in spring, which is checked 

 by the drouth of May and June. The rains of July and August, 

 ^diminishing toward October, stimulate the cambium into renewed 



* " Alalpais " is of Spanish derivation meaning " bad lands," and is ap- 

 plied to country covered with basaltic boulders, in these parts a very exten- 

 sive formation. Humboldt, 100 years ago, spelled it "malpays." 



