€l)c popular Science 0tXas 
AND 
BOSTON JOURNAL OF CHEMISTRY. 
Volume XXV. 
BOSTON^, APRIL, 1891. 
NUMBEB 4. 
CONTENTS. 
(Pamiliau Science. — Notes on the Later Life- 
History of tlie Flowering Dogwood . . 47 
Hieroglj'phic Inscriptions of Egypt and Pal- 
estine — How Read, and by Whom Discov- 
ered and Decipliered 48 
Photograpii of a Subaqueous Explosion . 49 
The Aquarium 49 
Genesis of the pjlements 50 
Electrical Heating , 50 
The Ginseng Family 51 
Edison's Explanation of the Ampere and 
the V^olt 51 
A New Method of Preparing Oxygen Gas . 51 
Industrial Jlemoranda 51 
IE Out-Door World. — Second List of 
Chapters and Members Agreeing to Keply 
to All Letters Received 52 
Chapter Addresses, New and Revised . . 52 
I An Interesting Letter and List of Plants and 
Insects from the Heart of Russia ... 52 
j The Agassiz Association Badge 52 
[ The Star of Bethlehem 53 
j Ottawa Houses 53 
The Legal Aspects of Hypnotism .... 53 
[ The Anatomy of National Life 53 
f Water Globules 54 
i Where Nature Plays Sculptor 54 
DITORIAL. — Harmony with the Environment 55 
' Photography in Colors 56 
Paris Letter 56 
Meteorology for February, 1891, with Re- 
view of the Winter 57 
Astronomical Phenomena for April, 1891 . .58 
Questions and Answers 58 
Literary Notes 58 
EDICINE AND PHARMACY. — Homeopathy in 
Relation to the Koch Controversy ... 59 
, Care of the Eyes of New-Born Infants . . 60 
t Monthly Summary of Medical Progress . . 61 
CBLiSHERS" Column 62 
familiar ^eienee. 
[Original In Popular Science News.] 
lOTES ON THE LATER LIFE-HISTORY OF 
ITHE FLOWERING DOGWOOD {Cornm Flor- 
: ida, L.) 
BY M. ALSTON READ. 
^The genus Cornus, to which the dogwood be- 
Qgs, is divided into two minor groups, one char- 
bterizeil by having "a head, or close cluster of 
reenish flowers, surrounded by a large and 
'showy, four-leaved, corolla-like, white or rarely' 
pinkish involucre; fruit bright red." The other 
has " white flowers in open, flat, spreading cymes ; 
involucre nou(^■' The object of this paper is to 
try and show the derivation of the first gi-oup, 
which consists of the flowering dogwood and the 
cornel (C Canadensis). The four large, white, 
petal-like expansions are not petals at all, but 
merely bracts — altered green leaves that grow 
near a flower. They form one of Nature's many 
devices for securing conspicuousness, in order to 
attract the attention of flower-loving insects, that 
they may eftect cross-fertilization for tlie plant, 
cross-fertilization being — as Mr. Darwin has so 
forcibly shown us — the great object of plant econ- 
omy. This is eftected by insects, which transport 
the pollen of one plant to the sensitive stigma of 
another. This beneficent act is not intentional on 
the part of the insect, but is simply a result of his 
flower-visiting propensities ; the pollen becomes 
entangled in his hairy coat, and thus gets carried 
to the flower next visited. 
The dogwood is a very showy and conspicuous 
plant in flower, and scarcely less so in fruit, as 
clusters of red berries gleam through the green 
foliage. It thus seems well endowed with at- 
tractive features. The flowering dogwood and 
cornel are probably recent oft'shoots from the rest 
of the genus, to which they bear uo resemblance 
to a casual observer ; for on the one hand we have 
what seems to be a single large white flower with 
a central head, and on the other we have a loose 
bunch of small white florets. 
f 
COENUS FLORIDA. 
Flower-bud. Flower-head. Terminal bud, protected by 
being enclosed In a sheath of the petioles. 
I said above that C. Florida and C. Canadensis 
were derived from the second group of the genus, 
and not the second group from them, for the fol- 
lowing reasons : - 
1st. These two form a much more specialized 
grouj), which means that they are later (the 
specializations are simply modifications of the 
family plan) and higher in the scale. They have 
crowded all their florets into a dense head, so that 
a large number can be fertilized at one visit, — as 
in the common daisy, — and thus a number of seeds 
set from a single visitation. 
2d. In the head the flowers are of different 
ages, there being some in which the stamens are 
ripe, and others in which the pistils are ripe. 
When an insect lights on this head he fertilizes 
those in thg second stage and gathers new pollen 
from those in the first stage, as he turns "round to 
suck the separate flowers in turn. 
3d. Because the majority of the plants of the 
same genus, as well as those of the allied families, 
are simpler and display the open cymose type of 
inflorescence. When you see a general, simpler 
type prevailing in several allied families, you may 
be sure tliat they, or their common ancestor, 
gained those characteristics before they broke up 
into separate groups or families. .\nd any small 
departure from them in the limits of a genus 
points to a more recent modiflcation. 
CORNUS FLORIDA. 
Flower-head, much enlarged, and with some of the florets 
removed, for greater clearness. 
The steps by which the dogwood and cornel 
reached their present state were, it seems to me, 
somewhat like these. 
llie species which, through some process of 
natural selection, first started towards the dog- 
wood, type, packed the florets of its cymose head 
closer together, and gradually reduced their num- 
ber. These two steps may be still observed, for 
in C. seriea the cymes are flat and close, and in C. 
stolonifera the cymes are small, flat, and few- 
flowered. In course of time four bracts began to 
assume the size, shape, and office of petals, in 
order to increase the showiness of the plant. 
There are numerous bracts scattered all through 
the cymes of the second group; especially near 
the edge they are larger and more numerous, as 
they are here less crowded out. (There are bracts 
surrounding the single florets, even of C. Florida) . 
These bracts are whitish green, which was proba- 
bly the original color of the white petal-like bracts. 
Concomitant with the development of these large 
bracts, the florets forming the head come closer 
and closer together. These l)racts now serve both 
as a protection and an attraction ; but at first they 
were, most probably, protective only, or largely 
so, and only later attained their white color.* 
These bracts are merely brownish gray scales 
in the bud, folded over the head of the true flow- 
ers ; and when they open they grow rapidly into a 
broad white expanse, still bearing the little scale- 
like part at the tip. The flowers themselves have 
become quite specialized, for, instead of having 
flat, spreading sepals and petals, like their nearest 
*At present the bracts in some cases show a tendency to 
pink, and seem struggling towards a higher scale in Grant 
Allen's scheme of progressive coloring; and if some insects 
confine themselves to the pinkish ones, we may in time have 
a pink species evolved. 
