450 BOTANICAL GAZETTE [DECEMBER 
During the summer of 1904 the maximum temperature at 2 P. M. 
observed in the superficial layer of soil on the little local deposits of weathered 
earth on the faces of cliffs, was 57° C. 
Occasionally the month of July is quite rainless. 
Some experiments on the amount of moisture contained in the material 
of the faces of tufa cliffs and walls gave the following results: 
Loss of moisture 
1904 at 100° C., per cent. 
Aug. 15. Top of Roman pillar of brick and tufa, portion about ultimate 
Pores Ot Bl epiaeo arbors. oO ee ee 
Sept. 1. Earth on face of cliff about ultimate rootlets of Artemisia 
ME ee a ee 
Sept. 8. Earth on face of cliff about ultimate rootlets of Matthiola rupe- 
WS ee a a ea ee ae ee 
Sept. 9. Earth on face of cliff about ultimate rootlets of Artemisia 
I oa eee ee 
Sept. 1o. Tufa-like clay, surface of cliff, no vegetation except Sedum sp. 0.7 
These determinations were made at a time when the autumn rains had 
not as yet set in, and the tufa and earth examined were nearly at their 
minimum as regards moisture-content. A few light sprinkles during late 
August and early September had not materially affected their condition. 
In the cliff-side formations about Pozzuoli the most important woody 
species, arranged roughly in the order of their abundance, are: 
1, Artemisia arborescens, L.; 2, A. variabilis, Ten.; 3, Helichrysum rupestre, 
DC; 4, Inula viscosa, Ait.; 5, Spartium junceum, L.; 6, Medicago arborea, L.3 
7, Opuntia Ficus-Indica, Mill.; 8, Mesembryanthemum acinaciforme, L.; 9; 
Matthiola rupestris, Guss. 
Number 5 of this list has been much discussed as a typical summer 
deciduous xerophytic shrub, and so it did not seem worth while to inves- 
tigate further its equipment for resisting the difficulties of its environment. 
Numbers 7 and 8, the succulent members of the formation, are not indige- 
nous and might better be studied in detail in their original habitats. ° Of 
the other members of this little flora it may be said that in general they 
have not the aspect of extreme xerophytes. It therefore seemed likely 
to be a profitable bit of work to look into the qualifications which 
most of the shrubs considered is the tufted form of the plant. Helichry- 
sum and Matthiola show this well in the shape of the plant as 4 whole 
