THE GARDENERS' CHRONICLE OF AMERICA 
13 
peting organisms tends to promote the growth of higher 
plants, and in general to create a better state of fertility. 
It should be pointed out that in the greenhouses, where 
conditions are continually favorable for their growth, 
such difficulties may become more acute than in the field 
where the variations in climatic conditions and the 
changes in season, including freezing in winter, tend to 
hold such processes in check." 
During the earlier periods of plant culture, the dealers 
in novelties were dependent on material introduced from 
foreign countries. These plants are still interesting many 
dealers. Within recent years, however, native haunts of 
ornamental plants have been so thoroughly gone over by 
the collectors that there are now fewer new species of 
value. Since this is true, plant growers and the intro- 
ducers of novelties have come to lay marked emphasis 
on the study of genetics, and this somewhat new subject 
has influenced the character of plant products to a 
marked degree. This influence has, however, been more 
pronounced in the changes of special characters because 
of changed environmental conditions, so that new varie- 
ties have interested our plant culturists. While some 
work in scientific plant breeding was done by Linnaeus, 
Koelreuter in the latter part of the eighteenth century 
laid the first real foundation of our scientific knowledge 
of the subject. Later, such names as Knight, Gartner, 
Darwin, Focke, De Vries, Mendel, Bateson and others 
stand out prominently in scientific literature relating to 
plant breeding. 
In their recent book on this subject, Bailey and Gilbert 
state as follows : 
"One of the 'signs of the times" in North America is 
the attention that is being given to practical breeding of 
cultivated plants. Lentil within a comparatively few 
years, however, breeding work has been unscientific in 
the extreme. Much of this has been because there have 
been few scientific principles which were tangible. 
Scientific experimenters are rapidly acctimulating results 
with many kinds of plants, and eventually there will 
probably be formulated definite statements as to how to 
proceed to secure desired results. However, there is no 
hope that plant breeding can ever produce forthwith the 
things that we desire, in the way in which the mechanic 
devises new machines, notwithstanding all the sugges- 
tions or persons who write with nnich self assurance. 
For all that we can now see, plant breeding will always 
be an exjjerimental process." 
It is then for men of science to formulate, through 
experimentation, the laws which govern heredity in 
plants so that practical growers may apply these insofar 
as possible in bringing out new and improved varieties. 
Present day scientific breeders of plants are, there- 
fore, not now working to produce new varieties so much 
as they are to discover, if possible, the laws which 
govern hereditary characters. Definite color and form 
inheritance, which may be expected by crossing dififerent 
plants, is of far more importance to the scientific mind 
than is the production of some commercial variety of 
plant which excels those now in existence. 
As has been stated, next to botany in its various di- 
visions, probably no branch of science has been more 
beneficial to floriculture than chemistry. Botany and 
chemistry are so interwoven in plant culture that it is 
impossible to state the relative importance of each. The 
application of chemical principles touches many phases 
of plant life closely. Both organic and inorganic sub- 
stances must be studied ; air, moisture and the soil ele- 
ments, which make life possible, are all intimately bound 
up in chemical substances. 
A study of the atmosphere in its relation to plant life, 
and of the soil in its relation to vigorous plant growth 
brings us closely into the chemical world. In earlier 
hcritcultural practice, little attention was paid to at- 
mospheric conditions. The air as a source of plant food 
was unthought of, for the plant growers of that early 
period had little to aid them in solving their problems 
regarding the source of material for improving the 
growth of their plants. 
For years there was a realization that the nature of 
the soil was important for healthy growth, but only 
within comparatively recent times has there come to be 
a realization that the atmosphere is equally important. 
Outdoor atmospheric conditions are little subject to con- 
trol, but in greenhouses the plants' environment in this 
respect may be more easily governed. With the dis- 
covery that a large jjercentage of a plant's substance was 
carbon, and that the plant received this carbon from the 
air, there came to be a better appreciation by plant 
growers of the fact that plants are as dependent on a 
liberal supply of fresh air as is man. The greenhouse 
builder, therefore, began to consider the principles of 
ventilation, and, although present day methods of green- 
house ventilation are extremely crude, nevertheless plant 
growth under glass is much more healthy than in the 
earlier days, when it was thought that all that was neces- 
sary was to give the plants warmth and light. Conse- 
quently, the early greenhouses were small and sunken 
in the soil so as to retain all the heat, and every possible 
effort was made to prevent the escape of warm air from 
the greenhouses, and to let little fresh, cool air in. Con- 
sequently the plants became so susceptible to fungous 
tliseases that it was almost impossible to grow many 
species. When the scientist showed the culturalist the 
value of fresh air. there was an improvement in the 
quality of the plants grown. Larger, airy houses were 
built, and these were located on more exposed elevations 
where good air circulation could be obtained and larger 
su])plies of fresh air were given the interior of the houses. 
The plant grower, however, is more concerned with 
soil and fertility questions than with almost any other 
problem in science. He grows a wide range of plant 
species, each with its own requirements, not only with 
the chemical constituents of the soil, but with the phys- 
ical character of the soil as well. It is generally known 
that plants under glass grow best if the soil contains a 
mixture of medium sand, silt and clay. The proportion 
of these varies with different crops, and all species re- 
quirements have to be studied carefully. They are 
learned largely by investigation and experimentation. 
Experiment stations in connection with the agricultural 
colleges and the United States Department of Agricul- 
ture have done nnich valuable scientific work in deter- 
mining correct conditions for various species of plants, 
yet much remains to be learned. 
Probably no cultivated plant is more particular re- 
garding proper physical and chemical constituents of the 
soil than is the rose. The best commercial rose growers 
in America today are those men who have kept closely 
in touch with the scientific work of the experiment 
stations. 
The chemist, and especially the agricultural chemist, 
is rendering valuable assistance to the flower grower. 
Unfortunately he is handicapped to a certain degree, 
and his limitations will not always permit him to fulfill 
the expectations of practical men. Only a few days ago 
the writer received a sample of soil, with the request that 
it be analyzed and the sender informed as to what he 
should apply to make it a good soil for violets. Many 
men fail to realize that all mineral elements must be 
rendered soluble before they can be used by plants, and 
that organic substances must exist in correct combina- 
tion before they are of value to plants. A soil may con- 
