784 NATURAL HISTORY MISCELLANY. 
ation by animals, through which fertilization and dispersion are 
subserved ? — Eps. ] 
PETALS IN ÅTRAGENE. — I have just taken a number of speci- 
mens of Clematis (Atragene) alpina which have well developed 
petals. In the subgenus Atragene, as is well known, the outer- 
most of the stamens are usually abortive, as if to represent the 
true petals, which are wanting. I have in one flower, not less 
than ten good petals, all of them being as long as the sepals, two- 
thirds as broad, and quite as deeply colored. 
These petals are all entirely destitute of any traces of the an- 
ther at their tips; nevertheless, in all the specimens in question, 
the transition from stamen to petal, is a gradual one, similar to 
what is seen in the flowers ọf Nymphcea. The usual four sepals 
are perfectly normal, and differ from the petals only in being 
broader.—Epwarp L. GREENE, Golden City, Col. Territory. 
TRANSPIRATION OF Leaves.—In the monthly report of the De- 
partment of Agriculture for March and April, 1871, page 149, is a 
short notice on transpiration of leaves. Pettenkofer is named as 
the observer, but he only made the report of the experiment, 
which was performed by Prof. Fred Pfaff in Erlangen. Being on 
a visit to Germany two years ago and standing under the same oak 
tree, which was the object of the observation, my old friend Mr. 
Pfaff explained to me his mode of calculations, which may be of 
interest to some of your readers. 
Cutting a small twig with the leaves, he brought it in a wide 
mouthed glass bottle, corked and weighed it. Then he exposed 
the leaves to the open air, weighed it again, after three to four 
minutes and marked the differences, from which he calculated the 
evaporation of the ‘leaves in a certain time. Then he outlined 
each of the leaves on fine paper, the weight and measure of which 
he had ascertained, cut the outlines out and weighed these again ; 
from the difference of weight he calculated the difference of meas- 
ute, and accordingly the surface of all the leaves. Afterwards he 
calculated the surface of the foliage of the whole tree in the fol- 
lowing manner: the crown of the tree was a regular elipsoid and 
easily measured ; deducting the inner leafless part, he found the 
bulk of the leafed part. Attaching cubes of different sizes, made 
of thin sticks representing the edges of the cube, to parts of the 
