172 CALIFORNIA ACADEMY OF SCIENCES. 



only 8 to 10 mm. long; the middle nerve is deeply marked 

 upon both kinds of leaves." (Bull. No. 5, 2d series, 

 Hayden's Geol. Survey of Terr., page 366.) 



In Heer's "Flora Fossilis Arctica" illustrations are 

 given of many fossil species. Sequoia Langsdorfii Heer, 

 the species apparently most widely distributed in past 

 ages, is similar to S . sempervirens, and the fossil speci- 

 mens show dimorphic foliage. (Flora Fossilis Arctica, 

 vol. ii, plate xliv, vol. iv, plates xiii-xiv.) The resem- 

 blance to S . sempervh'ens is quite evident. S . Reichen- 

 bachi Y{.Q.Q,x , vol. iii, plates xv-xxxvi, shows three forms 

 of leaves on the same branch. 



These go to prove that the genus Sequoia possesses a 

 tendency towards heteromorphism, which the environment 

 probably develops. 



Along the coast Sequoia sempervirens does not grow 

 above the altitude to which the moist sea air generally 

 rises — the fog-line, as it is often called. This is more 

 apparent near the southern limit of the species, which is 

 between Pt. Gordo and San Simeon Bay. The luxuri- 

 ance of the lower foliage may be due to the greater hu- 

 midity of the lower strata of the atmosphere, while the 

 stunted upper leaves indicate less nutrition. This view 

 is strengthened by the appearance of the upland trees 

 which begin to outgrow the distichous foliage when much 

 younger than the valley trees, and by the consideration 

 that the tall trees that rise to a height of two or three hun- 

 dred feet must reach an elevation which is often above 

 the fog, even when growing at a comparatively low alti- 

 tude. 



Nowhere is it more plainly shown than in California 

 that amount of moisture is the most important factor in 

 forest distribution. Many of the trees that abound near 

 the coast disappear in the dry hills of the southern Coast 



