876 



SCIENCE 



[N. S. Vol. XLII. No. 1094 



This is shown by plants cultivated from the spore 

 upon a elinostat revolving a horizontal plane. To 

 avoid error from single cultures, or from succes- 

 sive cultures on the same instrument or instru- 

 ments, a multiple elinostat has been devised, which 

 revolves forty or more turn-tables simultaneously. 

 This weight-driven multiple elinostat will be 

 shown to all interested. 



Discussion : MacDougal and Clements. 

 Theories of Photosynthesis in the Light of Some 

 New Facts: H. A. Spoehr, Department of Bo- 

 tanical Eesearch, Carnegie Institution of Wash- 

 ington. 

 The Distribution and Succession of the Flowers 

 of the Giant Cactus in Selation to Isolation: 

 D. S. Johnson, Johns Hopkins University. 

 The flowers of Carnegiea gigantea growing 

 about Tucson, are rarely symmetrically grouped 

 about the growing point of the massive stem. 

 They are usually most abundant on the east side 

 and least abundant, or wanting, on the west side. 

 If more evenly distributed about the circumfer- 

 ence, the flowers are larger and open first on the 

 east side. This is true of plants on all slopes and 

 of branches as well as of the main axis. 



The most evident external factors which may 

 be concerned with this peculiar distribution of the 

 flowers are sunlight and the air temperature. In 

 the season of hot days and cold nights, prevailing 

 when the flowers are developing, the morning sun 

 would increase the temperature, and so the rate 

 of grovrth on the east side of the crown first. The 

 high air temperature during midday would allow 

 this temperature of the east side of the cactus to 

 be maintained till late afternoon. The opposite or 

 west side, on the contrary, would probably not 

 reach its maximum temperature till mid-afternoon, 

 or later not long before the evening cooling of the 

 air sets in. 



Discussion: Lloyd, MacDougal and McCallum. 

 Demonstration by Peiree and McMurphy of 

 smelter smoke effects on vegetation. 



Thursday, August 5, 10 AM. 

 Factors Affecting the Distribution of the Com- 

 ponents of the Flora of California: Douglas 

 H. Campbell, Stanford University. 



1. The geographical position of California, 

 more or less shut off from the eastern states by its 

 mountains and the deserts, results in a flora very 

 different from that of other parts of the United 

 States. There is an unusual proportion of plants 

 peculiar to the state. 



2. The climate of California, especially the 



coast region, is dominated by the Pacific Ocean — 

 the climate, compared to Atlantic American, is 

 very mild and equable. Topography, rather than 

 latitude, regulates the temperature, e. g., there is 

 apt to be more difference between the maximum 

 of San Francisco and Sacramento, than there is 

 between Eureka and San Diego. 



3. Rainfall conditions show a wide range, exer- 

 cising a great influence upon its floras of different 

 parts of the state. Thus the flora of the redwood 

 belt of the northern coast has probably not a 

 single plant found in the arid district of the 

 southeast, like the Colorado desert. 



The prevalence of a dry summer throughout the 

 state results in the prevalence of " Xerophytes, " 

 i. e., plants adapted to withstand long periods of 

 drought. 



4. The remarkable range of conditions, i. e., 

 temperature, rainfall, elevation, soil, etc., results 

 in a variety of vegetation equalled in very few 

 parts of the world. 



5. The principal botanical regions are: (1) 

 The coast flora, (2) the redwood forest belt; (3) 

 the valleys, (4) the mountain region of the Sierra; 

 (5) the deserts of southern California. 



6. The plants of California show two distinct 

 types; a southern flora of Mexican origin, and a 

 northern flora more nearly related to the vegeta- 

 tion of the northeastern states. These two floras 

 mingle in the central part of the state, the north- 

 ern forms following the mountains southward, the 

 southern types mainly occupying the valleys. 

 There is a slight infusion also of Asiatic types 

 from the north. 



The B6le of Physical Features in Determining the 

 Distribution of Plants: Foeeest Sheeve, De- 

 partment of Botanical Eesearch, Carnegie In- 

 stitution of Washington. 

 The Chapparal and Its Habitat (illustrated) : W. 

 S. COOPEE, Stanford University. 

 The broad-sclerophyll vegetation of the Pacific 

 coast, as a dominant type, is confined to the re- 

 gion in which the long dry season, characteristie 

 of the California climate, is combined with low 

 total precipitation and absence of summer fog. 



The broad-selerophyll vegetation comprises two 

 formations: (1) the Oak-Madrofia Formation — 

 true forest; and (2) the Chaparral — bush or 

 scrub. Each is subdivided into various associa- 

 tions, the subdivisions being different in different 

 parts of the state. 



In the Palo Alto region the Chaparral includes 

 (1) the Adenostoma Association and (2) the Arc- 

 tostaphylos Association. The former is found 



