204 
POPULAR SCIENCE REVIEW. 
Professor Respighi has seen bright prominences upwards of 6 minutes 
high. As yet I have only seen one 5 minutes high, and that was faint and 
wholly detached like a little cloud. 
The depth of the stratum of hydrogen, called the chromosphere, is 4" or 
5" at the poles, and increases to 1" or 8" in the equatorial regions, where 
its surface is generally much disturbed and dotted all over with little 
tongues which are really minute prominences. 
^^The prominences seen at any instant may, of course, be very far from the 
true limb of the Sun. According to their height they are scattered over a 
zone of from 20° to 50° in breadth, as seen from the Sun’s centre.” 
BielcHs Comet and the Display of Meteors on November 27, 1872. — These 
subjects will be found fully discussed in another part of the present 
number. 
BOTANY. 
On Leaf ‘-arrangement. — A somewhat complex paper has been presented to 
the Royal Society, by Dr. H. Airy, on this subject. Those who are in- 
terested must consult the original paper, which is of some length [it was 
read on Feb. 27 last], but for ourselves we do not see much to support the 
author’s views. He says, assuming, as generally known, the main facts 
of leaf-arrangement — the division into the whorled and spiral types, and in 
the latter more especially the establishment of the convergent series of frac- 
tions, I, I, I, I, /j, 3^, II, If, jYj, &c., as representatives of a correspond- 
ing series of spiral leaf-orders among plants — we have to ask what is the 
meaning that lies hidden in this law ? Mr. Darwin has taught us to regard 
the different species of plants as descended from some common ancestor j 
and therefore we must suppose that the different leaf- orders now existing 
have been derived by different degrees of modification from some common 
ancestral leaf-order. One spiral order may be made to pass into another by 
a twist at the axis that carries the leaves. This fact indicates the way in 
which all the spiral orders may have been derived from one original order, 
namely, by means of different degrees of twist in the axis. Then, after a 
great series of examples, he concludes by stating we are led to suppose that 
the original of all existing leaf- orders was .a two-ranked arrangement, some- 
what irregular, admitting of two regular modifications, the alternate and 
the collateral ; and that the alternate has given rise to all the spiral orders, 
and the collateral to all the whorled orders, by means of advantageous con- 
densation in the course of ages. 
Preparmg Char^ for the Herbarium. — The calcareous-encrusted Charse 
make wretched herbarium-specimens, as is well known, being not only 
unsightly, but usually very fragile. M. Corum {vide Bull. Soc. Bot. Fr.,” 
xvii. p. 153) remedies this by plunging the fresh specimens for a short time 
in water containing one per cent, of hydrochloric acid, and afterwards wash- 
ing in pure water. Their aspect, when thus prepared and dried, is nearly 
that of the living plant. 
