w 
Vol. XXV. No. 7.] 
POPULAE SOIEIvTCE NEWS. 
lOS 
[Original In PopTjLAR Science News.] 
STUDIES IX PLAXT BIOLOGY. 
BY PROF. JAMES H. STOLLER. 
IV. 
THE MAIDEN-HAIR FERN. 
No plants that grow in the woods or waste 
fields are more noticeable than the ferns. The 
t.all feather-shaped fronds of the common species, 
met with everywhere in damp, shady places, are 
among the most familiar forms of vegetation. In 
almost any locality at least a dozen species of 
ferns may be found, and among them the maiden- 
hair fern {Adiantum pedatuyn), well known for its 
gracefulness of form and delicacy of structure. 
It may be distinguished from all others by the 
fact that the leaf-stalk is slender, highly polished, 
puiplish in color, and forks into two equal curved 
l)ranches, upon the divisions of which the small 
oblong leaflets are borne. 
It should be observed that the portion of the 
plant appearing above ground consists of the leaf 
only. The stem is under ground, being a rhizome ; 
it is dark colored, woody, branching. It remains 
iilive from year to year, growing w ith each season 
at one end of the main axis, and at the ends of the 
branches, and dying away at the other end of the 
axis. (It follows from this manner of growth 
that one plant eventually breaks up into many). 
From the growing ends each spring new leaves 
arise, those of the preceding year having died 
away at the approach of wintei'. Roots are given 
off from the lower side of the rhizome. 
Everyone who is observant of plant life has 
noticed that ferns, unlike other common plants of 
their size, do not bear flowers. It is generally 
known that the brown patches that appear on the 
under siiles of the leaves in late summer take the 
place — are the physiological equivalents — of flow- 
ers. Each of these patches, called a sorus, is 
made up of a number of box-like parts, termed 
sporangia, in which are contained spores. A spore 
is a single plant-cell, just large enough to be dis- 
cerned with the naked eye, consisting of a firm 
outer coat, or cell-wall, and soft contents of pro- 
toplasm. 
Let us trace the history of the spore produced 
by the maiden-hair fern. When, by the rupture 
of the sporangium, the spores have fallen to the 
ground, having been transported, perhaps, to 
some distance by the wind, they remain for some 
time — ordinarily until the next spring — in an in- 
active condition. l?ut the life of the tiny cell is 
consei-ved, and at last germination takes place, 
the spore giving ott" a slender thread-like projec- 
tion. This thread, by the formation of cross- 
partitions, comes to consist of a row of cells. 
I'resently it sends ofl' a downward-growing branch, 
which penetrates a little way into the soil. Thus 
a tiny plant, consisting of an above-ground por- 
tion, or thallus, and an underground portion, or 
root, is formed. Growth continues, and the aerial 
part, having increased both in length and breadth, 
comes to consist of a small, flat, heart-shaped 
green leaf. Meanwhile many additional hair-like 
roots have grown out from the lower side of the 
leaf, holding it to the ground and absorbing nour- 
ishment for it from the soil. This little plant, 
which is no more than about one-eighth of an 
inch in diameter, is called a prothallus. 
Thus the result of the development of the spore 
is the production of a tiny plant bearing no re- 
semblance whatever to the fern plant from which 
the spore was derived. We must look to see what 
becomes of the prothallus, to And out, perchance, 
how a new maiden-hair fern comes into being. 
If the little green leaf be closely examined there 
will be seen upon its lower side small elevations 
of two kinds. Those of the one sort are rounded 
in fonn, numerous, and placed among the root- 
hairs, at their bases ; those of the other kind are 
larger, flask-shaped, and situated near the notch 
in the middle of the wide end of the leaf. Exami- 
nation of the rounded elevations shows that within 
them a number of cells are developed, and by con- 
tinued observation ]f. may be. ascertained that 
these cells become changed to spirally-coiled, cil- 
iated bodies, which emerge from thin covering 
and swim about in the drop of rain or dew that 
may be adherent to the leaf. These bodies are 
antherozoids, or male reproductive cells. In the 
flask-shaped elevations a single, relatively large 
cell develops, the oosphere, or female reproductive 
cell. The motile antherozoids make their way 
through the neck of the flask, and, uniting with 
the oosphere, eflect its fertilization. 
lliis cell is now the germ of a new plant. It 
soon begins to divide, and, by the usual process 
of cell-multiplication and differentiation, ulti- 
mately develops into the familiar fern plant. The 
prothallus exists only for a short time — passing 
away as soon as it has afforded nourishment for 
the primary stage of growth of the fern. Thus 
the office of the prothallus is the development of 
the sexual reproductive cells. The .spores pro- 
duced on the leaves of the fern in summer, while 
truly reproductive cells, are lacking in any char- 
acter of sex. Tliey serve only to produce a thal- 
lus upon which are formed the tnie sexual cells. 
Plants going through a round of life like that of 
the ferns are said to exhibit alternation of genera- 
tions. By this is meant the alternation of a sex- 
ual with an asexual generation. This ijrin'ciple of 
alternation is true of most of the cryptogamic, or 
non-flowering plants; and it is perpetuated, in 
indistinct form, in the higher flower-producing 
plants. 
If a thin cross-section of the stem of a fern leaf 
be examined with the microscope, it presents a 
very pretty appearance, and also aflbrds a means 
for gaining a knowledge of tissue-structure as 
seen in i)lants. One sees that the stem is made 
up of cells, the appearance as a whole being like a 
piece of delicate lacework. A little observation 
shows that the cells are of several different kinds, 
in regard to shape, size, and thickness of walls, 
and that those of the same kind are arranged in 
groups. 'Ilius at the outside of the stem are 
small, thick-walled cells, and it may be readily 
inferred that these are protective for the cells 
within, and that they give to the stalk its hard- 
ness and strength. These cells thus form an 
epidermis, or protective and supporting tissue. 
Within the epidermis, and making up the greater 
part of the section, are rather large cells, polygo- 
nal in shape, with thin walls, and having granular 
contents, which, upon being tested, proves to be 
starch. lliese cells form the parenchyma, or 
nourishing tissue. In the stem of a young fern 
the parenchyma cells are green in color, due to 
the presence of chlorophyl, and at this time they 
perform the function of starch-makers. But as 
soon as the leaves are fully formed, this work is 
mainly transferred to them. The starch present 
in the parenchyma cells of the stem of tlie fully 
grown plant has, in part, been brought down from 
the leaves, and is stored up in the cells as food- 
matter, available for the living cells of every part 
of the i^lant. 
In the middle portion of the stem one sees a 
large group of cells forming a third kind of tissue, 
or rather a system of tissues, namely, fibro-vascu- 
lar bundles. Some of the cells of these bundles 
are much elongated and placed end to end, form- I 
ing vessels, for the transfer of gases and liquids 
through the plant-body. Other cells are smaller, 
thick-walled, and are packed around the vessels ; 
these are called fibers. Of these vessels and fibers 
there are to be distinguished those which are 
associated to form the xylem, or wood part of the 
bundle, and those which form the phlmm, or bast 
portion of the bundle. 
In the possession of these several tissues the 
ferns approximate in organization the higher 
flower-bearing plants. In the scale of plant life 
the ferns stand somewhat above the middle place. 
That this is their relative rank is also indicated in 
the fact that the ferns and tlieir allies were char- 
acteristic of the middle periods of geologic time. 
Union College, Schenectady, X. Y. 
[Specially Observed for Popular Scibncb News.] 
METEOROLOGY FOR MAY, 1891, WITH 
REVIEW OF THE SPRING. 
temperature. 
Average Thermometer. 
Lowest. 
Highest. 
Range. 
AtTA.M 
At2P. M 
At9P. M 
51.62° 
66.4.5° 
■ 54.00° 
38° 
50° 
40° 
38° 
38° 
68° 
84° 
66° 
84° 
84° 
30° 
34° 
26° 
Whole month .... 
Second average . . . 
67.32° 
56.49° 
46° 
46° 
Last 21 Maya .... 
Second average . . . 
57.62° 
56.82° 
1 51.34° 
i In 1882. 
50.67° 
64.28° ) 
In 1880. i 
63.64° 
12.94° 
12.97° 
Spring of 1891 .... 
Last 21 Springs . . . 
46.67° 
45.21° 
3° 
( 42.16° 
i In 1875. 
84° 
49.48'" ( 
in 1889. i 
81° 
7.31° 
The most remarkable feature of the last month 
was its dryness, as shown below. The tempera- 
ture was a near average. The lowest point of the 
mercury, at the hours of observation, was .38°, on 
the mornings of the .5th and 6th, when frosts 
appeared, doing considerable damage in some lo- 
calities, as also on a few other mornings. Tlie 
5th was the coldest day, with an average of 42.60°. 
There were several cool spells, which seemed to 
check vegetation. The 11th and 31st were the 
warmest days, each averaging 68.33°, the highest 
point (84°) being on the 11th. There were several 
warm as well as cool spells. TTie daily extremes 
in the last twenty-one Mays have been 33° in 1873, 
and 91° in 1880,— a range of 58°. The monthly 
extremes and range are shown in the table. 
The mean temperature of the present spring 
(46.67°) was nearly 1.5° above the average. The 
daily extremes in twenty-one springs have been 
—4° in 1872, and 91° in 1880,— a range of 95°. 
SKY. 
The face of the sky, in 93 observations, gave 50 
fair, 20 cloudy, 16 overcast, and 7 rainy, — a per- 
centage of 53.8 fair. The average fair for the last 
twenty-one Mays has been 54.4, with extremes of 
only 29.0 in 1888, and 78.5 in 1871,— a wide range. 
The average fair the last spring was 54 per 
cent., while that of the last twenty-one springs 
has been 52.3, with extremes of 41.7 in 1884, and 
63.0 in 1872. 
PRECIPITATION. 
The amount of rainfall the last month was only 
1.37 inches, of which .95 inch fell on the 16th, and 
.35 on the 29th, leaving but .07 inch for the rest of 
the month. Tliis scanty amount was preceded by 
only .17 inch in the last half of April, making a 
period of fully six weeks, when vegetation most 
needs rain, of unusually dry weather. The sever- 
ity of the drouth must have been lessened by the 
abundant precipitation during the months imme- 
diately preceding. The average rainfall the last 
