50 
POPULAR SCIENCE NEWS. 
[Ai'itiL, 1S90. 
To fully discuss these laws would require inany 
pages, but for our present purpose it will be enough 
to point out that the various. sorts of leaf arrange- 
ment on vertical axes are approximations — often 
extremely close — to that method which mathema- 
ticians have found to be theoretically best for 
securing to each leaf the utmost exposure to sun- 
light, and, at the same time, having it shade the 
others as little as possible. Thus, on stems having 
the leaves opposite, the successive pairs cross at 
right angles, and so each leaf has a clear space 
above it and also one below. In other cases, the 
leaves are arranged spirally around the stem, like 
the steps of a winding stair-case, and alwai'S with a 
nice adjustment of distance, angle, size, and propor- 
tions of leaf. 
Fig. 4. Sycamore Maple. (Kerner.) 
Besides these more common instances of leaves 
situated in higher and lower planes, there not 
infrequently occur occasions when it is of advantage 
to a plant to have all its leaves — or, at least, all the 
leaves of a branch — spread out at nearly the same 
level. Then the best possible disposition of the 
leaf-blades becomes a sort of mosaic, in which all 
the available space is completely filled, and without 
overlapping. Almost any wood or country road- 
side will afford examples of leaf-groupings which 
meet these conditions in ways as beautiful as they 
are interesting, and if a person is on the lookout for 
them, he will have many delightful surprises. 
In situations where the soil is poor, and where, 
consequently, as much of the ground as a plant can 
get is none too much for its needs, we find leaves 
disposed in flat rosettes, (like that shown in Frg. i), 
which effectually exclude all rivals from the area 
they cover. Plantains, dandelions, mulleins, and 
saxifrage afford other familiar examples. But, in 
the power to exclude other plants from the soil it 
occupies, we have no weed which equals one which 
southern farmers call "the king devil." Not con- 
tent with poor soil, it encroaches upon cultivated 
fields with such rapidity that, in a single season, 
acres will be covered with an almost continuous 
mat of the outspread leaves. 
Similar in many ways to these rosettes on land, 
are those made at the surface of ponds and strearris 
by clusters of floating leaves, borne on more or less 
elongated foot-stalks which come from a submerged 
stem. The water-starvvort (Fig. 2) is a pretty little 
plant of this description, and abounds during the 
spring and summer. 
Finally, in shady woods we find a third form of 
rosette (Fig. 3), consisting of a circle of leaves 
placed at the top of a short, upright stem, and so 
rather suggestive of a parasol. Since the theoreti- 
cally best form for the leaves composing a rosette is 
a sector of greater or less width, according to the 
number of leaves, it is interesting to notice how 
nearly sector-shaped many of the rosette leaves 
actually are. 
In the case of trees and shrubs, a mosaic-like 
arrangement of the leaves becomes of advantage on 
those branches which take a horizontal direction, 
and, if these happen to grow in a shady situation, it 
becomes all the more important for the leaves to be 
so disposed that they may utilize to the utmost 
what little light they can get. A moment's consid- 
eration will show that this little piece of engineer- 
ing, which leaves have so often to perform, is by no 
necessity of adjusting them to each other with 
considerable nicety. 
Thus in the maple (Fig. 4) we have a case in 
which the leaves arise in pairs, crossing each other 
as before described. Consequently, to make the 
blades horizontal on a lateral branch, certain of the 
leaf-stalks have to twist through half a turn, while 
others are forced to bend through 90^'. But, 
besides this, there is a lengthening of some of the 
stalks, by which means the blades are carried out 
of shadow, while other stalks are correspondingly 
shorter than the average, so that they will shade 
only the stem. Finally, it should be noticed how 
well the size of each leaf is adapted to the place it 
occupies, and how admirably the peculiar angular 
shape allows them to fit together. 
This fitting together of angular shapes is, how- 
ever, accomplished even better by the English ivy 
(Fig. 5), and the result, as will be seen, is an 
especially fine mosaic. The hazels, blueberry- 
bushes, and the elm (Fig. 6), especially when 
growing in the shade, exhibit the effects of similar 
twistings and bendings, and show also the filling of 
means so simple as might appear at first sight. 
To start with, all the leaves on a plant have funda- 
mentally the same arrangement, and, most com- 
monly, this is such as was described above for 
vertical stems. Hence, to bring into one mosaic- 
like cluster a number of leaves which tend to point 
Fig. 6. Elm. (Kerner.) 
away from the axis in all directions, a variety of 
expedients must be resorted to ; and even when they 
are brought to lie in one plane, there rernains the 
(Kerner.) 
small spaces with small leaves. In the Chinese 
honeysuckle such small leaves make their appear- 
ance on the older parts of a shoot — a single pair at 
the base of each leaf-matter the first leaves have 
attained their growth, and are thus actually inter- 
calated to fill up, as well as may be, the remaining 
spaces. This introduction of small leaves into a 
mosaic is well exhibited also in the belladonna (i), 
and in a somewhat different way in certain species of 
selaginella (2, Fig. 7.) 
Climbing plants, like this honeysuckle and the 
ivy, and others which grow closely appressed to the 
upright face of rocks, walls, or tree-trunks, differ, as 
a rule, from the other plants we*have described, in 
having their leaves vertical instead of horizontal, 
and plenty of cases may be found of leaves grouped 
in planes more or less oblique ; but in every instance 
it will be seen that only one side of the leaves is 
well illuminated, and this is clearly the essential 
condition for the formation of a leaf mosaic. 
A Curious Mental Trait. — A correspondent of 
the German Anthropological Society tells of his 
meeting a farmer by the name of Lowendorf, who 
had a peculiar habit of writing "Austug" for 
"August," his Christian name. Some years later 
he was inspecting a school, and heard a little girl 
read "leneb" for "leben," "naled" for "nadel," 
and the like. Upon inquiring, he found that her 
name was Lowendorf, and that she was a daughter 
of his former friend, the farmer, now dead. This 
defect was noticeable in the speech and writing of 
both father and daughter. It appeared in the father 
as the result of a fall that occurred some time before 
the birth of his daughter. 
