910 
purple color. One most commonly sees in 
a state of nature the white heads which are 
tinted with lavender or pale purple at the 
base of the ray floret. The heads in each 
ease are nearly uniform in size, being about 
an inch and three-fourths across. 
There are several other species worthy of 
mention. Dahlia imperialis, D. scapigera, 
D. dissecta and D. pubescens. Dahlia dissecta 
was discovered by Mr. C. G. Pringle grow- 
ing on limestone ledges fifty miles east of 
San Luis Potosi. ‘It is a very unique 
species, being scarcely more than two feet 
high and of bushy habit from an almost 
woody base.” The flower heads are two or 
three inches broad, with about eight mauve 
colored rays. Dahlia pubescens was found 
by the same botanist on calcareous bluffs of 
prairies bordering the valleys of small 
streams in the State of Mexico and to the 
north of Toluca. It isa small plant, one 
and a-half to two feet high, with heads two 
to three inches broad, with a yellow disc 
surrounded by eight rays which are purple, 
with lines of deeper color which changes 
with age to light purple or dull rose. 
The tubers of these plants, particularly 
those growing on the lava beds along the 
southern mountainous rim of the Valley of 
Mexico, are hard to obtain, because of the 
depth to which they sink in the lava 
pockets. All of the species store up in 
their tubers a substance called inulin, 
chemically allied tostarch. The substance 
is in solution in the cell, much as sugar is, 
but crystallizes out in needle-shaped crystals 
upon the addition of alcohol. This sub- 
stance is stored up as a reserve food to meet 
the demands of the plant during the active 
growing season, and the tubers with this 
stored substance perpetuate the species dur- 
ing the long droughts which are frequent in 
Mexico. 
The dry season in the region of the Val- 
ley of Mexico lasts from about the first of 
October until about the first of June, when 
SCIENCE. 
(N.S. Vox. VI. No. 155. 
there are signs of the returning rainy sea- 
son. During thedrought the tubers of the 
Dahlias lie dormant until the first rain 
moistens the soil, when they spring up in 
great numbers everywhere on the lava beds. 
The plants grow vegetatively until the end 
of August, when they flower in the greatest 
profusion. The rainy season is character- 
ized in the Valley of Mexico by afternoon 
thundershowers. The morning will be cool, 
and the air bracing, until evening, when the 
sky becomes overcast and the rain comes 
down sometimes in torrents. 
A consideration of these meteorological 
conditions ought to influence the cultiva- 
tion of the Dahlia, which has not been en- 
tirely understood. It will repay some 
energetic nurseryman to obtain fresh 
tubers directly from the mountains of 
Mexico by a personal visit to the native 
home of the plant. It will repay him to 
collect tubers of every plant with a differ- 
ent shade of color. As already intimated, 
the plants in a state of nature are extremely 
variable. This variation in nature, as com- 
pared with the variation produced by culti- 
vation, is just as striking, and shows us 
that many of thespecies are in an extremely 
unstable state of equilibrium as regards their 
plasticity. This great plasticity in a state 
of nature explains how so many new colors. 
and forms originated, almost asif by magic, 
when the Dahlia was first introduced into 
cultivation. The inherent possibilities of 
color and form were represented in the 
protoplasm, and only needed the stimulus 
of a varied culture to bring out these latent 
acquired characteristics. 
Joun W. HARSHBERGER. 
UNIVERSITY OF PENNSYLVANIA. 
CURRENT NOTES ON ANTHROPOLOGY. 
INSCRIPTION OF THE CROSS AT PALENQUE. 
Tus most famous of all the Mayan in- 
scriptions has been subjected toa searching 
analysis by Dr. Forstemann (in Globus, Vol. 
