64 CARNEGIE INSTITUTION OF WASHINGTON. 



It seems not unlikely that considerable quantities of carbon dioxide 

 are dissolved in or in some way occluded by the fleshy tissue. A 

 determination of the CO2 content of such tissue under varying con- 

 ditions is in progress. It is evident that the processes involved are 

 at least somewhat dissimilar from those presented by the succulent 

 tissue of the cacti. 



The gas samples taken this year were preserved, as before, for 

 later precision analysis, but during the progress of the experiments 

 proximate analyses were made by a simple method that gave results 

 accurate perhaps to 0.25 per cent. These supported the results pre- 

 viously obtained, but must of course be checked up by more careful 

 determinations. 



A considerable number of series of determinations were made of 

 the acidities in leaves of different degrees of maturity. In the case of 

 the terminal buds of the two common forms of Mesembryanthemum 

 found at Carmel, there are at the tip usually two small leaves, while 

 those immediately below are practically fuU-grovm. It was found 

 that the total acidity of the small terminal leaves was 1.20 c.c. N/20 

 KOH per gram fresh weight, while in the older leaves immediately 

 below and the others farther back the total acid content was 0.60 

 c.c. N/20 KOH. 



Similarly, in Dudleya farinosa the youngest leaves in the center of 

 a rosette showed a total acidity of 3.00 c.c. N/20 KOH per gram fresh 

 weight, while in the fully mature leaves the acid-content was only 

 2.25 c.c. N/20 KOH per gram fresh weight. The intermediate leaves 

 showed, with some variation, intermediate acidities. That such should 

 be the case is not surprising and is entirely consistent with the 

 results obtained by Dr. D. T. MacDougal in his swelling measurements, 

 but as far as the present work is concerned it indicates that for like 

 results it is important to select tissues of like acidity. 



Acidity of Mesophytic and Succulent Forms of Castilleia, Ericameria, and 

 Erigeron, by H. M. Richards. 



Some interesting forms of variation in degree of succulence of 

 certain of the plants which grow on the foreshore and edge of the 

 beach were found and their acidities and relative dry weight were 

 determined. Thus in Ericameria ericoides, a common shrub near the 

 sea-front, the foliage of the typical form is dark green and the linear- 

 terete slightly hirsute leaves average 4 to 6 mm. long by 0.5 mm. 

 thick, while a form growing on the cliff- edge overhanging the beach 

 is yellowish green in color, with more glabrous leaves that are from 

 2.5 to 3.8 mm. long by 0.75 mm. in thickness. The total acidity and 

 dry weight per gi-am fresh substance of the typical form are 2.70 

 c.c. N/20 KOH and 0.35 gram, respectively, while in the succulent 

 type the total acidity is only 1.30 c.c. N/20 KOH and the dry weight 



