136 
POPULAE SOIEiq"CE l!TEWS. 
[September, 1891. 
tity has escaped. To remedy this fault it has 
been proposed to add a minute trace of mercap- 
tan — a sulphur compound of an extremely offen- 
sive odor — to the gas. While this would not 
injure its illurainatiug qualities in any way, and 
would be perfectly inoffensive after being burnt, 
it would make its presence at once manifest in 
case of any accidental escape of the gas, and lead 
to the prompt repair of the pipes. 
In Massachusetts the amount of carbonic oxide 
in illuminating gas is forbidden l)y law to exceed 
a certain per cent. ; consequently the use of water 
gas in the State is very limited. In most States, 
however, there is no restriction upon its composi- 
tion, and the only reason that water gas has not 
come into almost universal use is probably due to 
the small diffei^ence between the cost of its pro- 
duction and that of gas distilled from coal in the 
old-fashioned way. 
[Original In PopuLAK Soiehce News.] 
STUDIES IN PLANT BIOLOGY. 
BY PROF. JAMES H. STOLLER. 
V. 
THE SCOTCH PINE. 
The plants to which special reference has been 
made in these studies, thus far, are members of 
groups which together constitute the primary di- 
vision Cryptogamia. The early botanists, observ- 
ing that of the common plants some bear flowers, 
giving rise to seeds, while others are destitute of 
flowers, reproducing themselves through spores, 
naturally divided the plant world into two great 
groups corresponding to these dift'ei-ences. Lin- 
naeas, the father of botany as a formal science, in 
the system of classification which he presented in 
1737 adopted the names Cryptogamia and Phmnero- 
gamia to designate these primary groups. But 
modern botanists recognize that the plant king- 
dom is not thus divided in Nature into two dis- 
tinct groups. There is no sharp line of demarca- 
tion between the highest spore-bearing plants and 
the lowest seed-producing plants. Here as every- 
where in Nature there is gradation, and the one 
series merges into the other. We shall present 
below the facts upon which this conclusion rests. 
Our present study relates to the first great class 
of the Phcenerogamia, namely, the Gymnosperms. 
As a type-form of the class we cite one of the 
pines, Finns sylvestris, known commonly as the 
Scotch pine. Other gymnospermous plants are 
the flrs, cedars, cypresses, larches, yews, etc., 
commonly spoken of as evergreen trees. The 
Scotch pine is a tree of moderate size, possessing 
a central main trunk and a crown of several large 
and many small branches. The bark is rough, 
due to the scaling off of the outer layers, and is 
of a reddish brown color. The leaves are needle- 
shaped, and are arranged in pairs, each pair being 
attached to a short side branch. The leaves and 
the bark of the young branches are sticky to the 
touch, due to the presence of resin — a secreted 
product characteristic of the order of cone-bearing 
plants. 
When we speak of a gymnospermous plant as a 
flowering plant, we use the term flower in its bo- 
tanical sense, as an organ destined to produce the 
seed. In the Scotch pine the flowers are in the 
form of cones, and each plant bears cones of two 
kinds. In early summer there may be seen on the 
lower parts of the youngest shoots clusters of 
perhaps twenty or thirty cones of small size. If 
the small scale-leaves which make up the cone 
structure be examined, they will be found to bear 
on the lower surface two minute sacs. These are 
pollen sacs, containing the pollen, or male repro- 
ductive cells. Hence these small clustered cones 
are the staminate flowers of the plant. The other 
cones are larger, and are borne singly at the ends 
of the small branches. Each is made up of a 
number of greatly thickened scale-leaves, ar- 
ranged in rows about a central axis. Each of 
these scales is found to bear, at the proper season 
of the year, on the inside near its base two small 
sacs, which are ovules. Thus these cones are 
pistillate flowers. When the ripened pollen sacs 
open and shed their pollen, the scales of the pis- 
tillate cone separate and allow the pollen to fall 
upon the ovules. Some of the pollen cells then 
give oft" a delicate sprout, the pollen tube, which 
enters the ovule through a minute opening in its 
surface, the micropyle, and thus the fertilization 
of the embryo vesicle of the ovule is effected. 
Development of the ovule then takes place until 
at last it has become a seed. 
It is characteristic of the Gymnosperms that 
their flowers, as we have seen in the Scotch pine, 
are of very simple structure. The ovules of the 
female flower are not enclosed in a protective 
case, or ovary, as in the higher class of flowering 
plants. It is this feature that gives the name 
Gymnosperm (naked seed) to the class. Moreover, 
the flowers do not possess showy or nectar-bear- 
ing parts, but consist simply of leaves modified in 
form and size, upon which are developed the spe- 
cial sexual parts. 
Let us now endeavor to see clearly the essential 
identity between the highest grade of flowerless 
plants and the lowest grades of flower-bearing, 
seed-pi-oducing plants. In the last paper we 
learned that the fern plant produces spores which 
upon germination give rise to the prothallus, or 
asexual generation of the plant, which develops 
the reproductive cells. Now there is a class of 
cryptogamous plants, including the not uncom- 
mon aquatic plants called quillworts, which pro- 
duce not one but two kinds of spores, called mi- 
crospores and macrospores. The microspores, 
when they germinate, give rise to a prothallus 
which produces the male reproductive cells ; and 
the macrospores grow into a prothallus which 
develops female cells. The two kinds of sexual 
cells come into unison, ^ — connection being ef- 
fected, as in the ferns, by the swimming action 
of the male cell, — and a germ cell is produced, 
from which a new asexual plant is derived. 
Now in the flowering plants there are produced 
parts which correspond to these in the highest 
non-flowering plants. The familiar pollen grains 
are the homologs, or physiological equivalents, of 
the microspores ; and the embryo sacs which are 
present in the ovules correspond to the macro- 
spores. The one-celled pollen grains, in the case 
of some of the lowest phaenerogams, develop into 
a several-celled stage which is the homolog of the 
prothallus formed by the microspore of the high- 
est cryptogams. Similarly the embryo sac pro- 
duces the endosperm, which is the equivalent of 
the prothallus developed from the macrospore. 
Finally, the pollen tube which grows out from 
the pollen prothallus in these plants, and the 
germinal vesicles which form within the embryo 
sac, are the sexual cells of the flowering plant, 
corresponding to the antherozoids and the oospores 
of the prothalli of the cryptog.amic plant. 
Thus it is that the only important difference 
between the two groups is that in the cryptogams 
the spores produced by the asexual generation of 
the plant become separated from it before devel- 
oping into prothalli, while in the phajnerogamous 
plants only the microspores (pollen grains) be- 
come separated, the macrospores (embryo sac) 
developing a prothallus (endosperm) while in 
connection with the plant which bore it. 
The close connection between the two groups 
thus rendered evident by a study of their repro- 
ductive organs, is borne out by a comparison be- 
tween them in regard to the kinds of tissues, or 
cell-groups, which enter into their composition. 
For instance, if we compare the leaf of a fern with 
that of any common flowering plant, as the but- 
tercup, we find thiit while the two difter greatly 
in general form, they are yet very similar in tissue 
structure. In both there are present an epidermae, 
a parenchymous, and a vascular tissue. In both 
there are present in the leaves small openings, 
called stomata, which afford communication be- 
tween the outer air and the interior of the leaf. 
In both the framework of the leaf consists of 
fibro-vascular bundles which extend into the 
branches and thence into the main axis down to 
the roots, thus affording an interchange of gases 
and fluids between the leaves and the roots. 
Union College, Schenectady, N. Y. 
[Original In POPULAR SCIENCE NEWS.] 
POTATO CULTURE. 
An important contribution to agriculture has 
been recently brought out in France by M. Aime 
Girard. Although it concerns experiments and 
results obtained in France only, as yet, the facts 
and conclusions are of so very general character 
that they doubtless apply to all countries, — pota- 
toes surely have no nationality ! — and must be of 
great interest for American farmers. The aim of 
M. Aime Girard, in his Becherches sur la Culture 
de la Pomme de Terre Industrielle et Fourragere, 
(Paris, Gauthier-Villars, 8 francs), is to show that 
potato culture, as it stands at present in France, 
can be largely perfected, so as to yield the largest 
crops possible. Potato culture in France occupies 
the fourth place in agriculture — wheat, fodder, and 
the vine coming before. It extends over 1,454,794 
h,ectares,{i\\e. hectare is about two and a half acres), 
and represents .350,000,000 francs,— a very misera- 
ble state of affairs, since the hectare yields only 
260 francs benefit (§53.00). This is due to the 
fact that the ci'ops are small. While England ob- 
tains 15,000 kilogr.ams of potatoes to the hectare, 
Belgium 12,000 or 13,000, and Germany 9,000 or 
10,000, and sometimes 20,000 or 30,000, France has 
only a little over 7,000 kilograms. Such being 
the condition of att'airs, M. Girard has been work- 
ing for some five or six years in order to ascertain 
whether better crops cannot be obtained ; and the 
result is that the thing is quite feasible, if certain 
conditions which he .advises to observe are strictly 
kept. The fact that new methods of culture are 
apt to yield better results, may be as true in 
America as in France, and therefore some words 
may be said concerning the methods. 
The basis of the new method consists in some 
facts concerning the physiology of the potato and 
of its growth. For, while it certainly is always 
better to secure the best stock or variety among 
the numerous existing ones, the excellence of the 
stock has nothing to do here : the results are the 
same for all varieties, mutatis mutandis, of course, 
and keeping an account of their peculiarities, 
preferences, etc. Studying the growth of the 
potatoes, M. Girard ascertains that this growth 
and increase in weight goes on as long as there 
remains a single green leaf on the plant, and that 
the same is true of the production of starch in the 
tubers. And there is an important relationship 
between leaves and tubers : the more abundant 
the leaves are, the more abundant is the produc- 
tion of starch. Starch originates indirectly in the • 
leaves; the sacch.arose of the leaves goes to the 
l)Otatoes and then becomes starch. It would re- , 
quire too much space to go into the details of j 
