Botany As An Experimental Science

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BOTANY AS AN
EXPERIMENTAL SCIENCE

IN LABORATORY AND GARDEN

OXFORD
UNIVERSITY PRESS

AMEN HOUSE, E.C. 4
London Edinburgh Glasgow
New York Toronto Melbourne
Capetown Bombay Calcutta

Madras Shanghai
HUMPHREY MILFORD

PUBLISHER TO THE
UNIVERSITY

BOTANY AS AN
EXPERIMENTAL SCIENCE

IN LABORATORY AND GARDEN

By

LILIAN J. CLARKE
D.Sc. (LOND.),

FORMERLY HEAD OF SCIENCE DEPARTMENT
JAMES ALLEN'S GIRLS' SCHOOL, DULWICH

OXFORD UNIVERSITY PRESS
LONDON : HUMPHREY MILFORD

1935

'In my laboratory I find that water of Lethe which causes
that I forget everything but the joy of making experiment*

ROBERT BOYLE

'In a great variety of articles very young persons may
be made so far acquainted with everything necessary to be
previously known as to engage (which they will do with
peculiar alacrity) in pursuits truly original.''

JOSEPH PRIESTLEY, 1774

PRINTED IN GREAT BRITAIN

PREFACE

BOTANY at the James Allen's Girls' School for many years
has been taught by means of observations and experiments
made by the girls themselves in laboratory and garden.

No text-books are used until post-Matriculation work is
reached. The girls make their own books, and in them are re-
corded not only the results of their own experiments, but the
results of hundreds of other experiments made during the
course of many years.

It is wrong in biological work, as in other branches of science,
to generalize from a few facts. Professor Batcson, in the Huxley
Centenary number of Nature said: 'No one better than Huxley
knew that some day the problems of life must be investigated by
the methods of physical science, if biological speculation is not
to degenerate into a barren debate.'

Of biological science Huxley said: 'The subject-matter is
different from that of other sciences, but the methods of all are
identical; and these methods are:

1. Observation of facts, including experiments.

2. Comparison and classification, the results of the process

being name^^enSi^l^ypositions.

3. Deduction.

4. Verification.

Such are the methods of all science whatsoever.'
The time allotted to a lesson at J.A.G.S. is often short, but
if the results of experiments are recorded, year after year, there
can be accumulated a mass of evidence to which reference can
be made. But the reference should not be made until after the
members of a class have made their own experiments, and the
results have been summarized. In this way there can be a
training in scientific method as well as a discovery of facts.
There is the training in manipulation, in recording results, in
comparing individual results with those obtained by others, and
in drawing conclusions from a great number 4 of facts. Any
results which differ from the majority are not slurred over,
but carefully examined, and possible explanations of the dis-
crepancies are often suggested by the girls themselves.

vi PREFACE

There are recorded at J.A.G.S. the results of more than
4,000 experiments made to see if pollen is necessary for the for-
mation of fruit. The leaves of more than 350 species have been
tested to see if they form starch in the light, and nearly 300
experiments have been made to see if there are pores in leaves,
and if so, how they are distributed.

Since the end of last century more importance has been paid
at the James Allen's Girls' School to the plant as a living
organism than to any other branch of Botany. As a rule the
experiments are made by the girls themselves, every girl, either
alone, or with a partner, setting up and carrying out the experi-
ments in the laboratory or garden. The only exceptions to this
in pre-Matriculation classes are those experiments involving the
use of a clinostat or auxanometer, and those showing the
respiratory coefficient, anaerobic respiration, and the growth of
the root into mercury.

It must be remembered, however, when examining the results
of experiments, that these experiments have been made by
young inexperienced girls, often with very simple apparatus,
and that the time in which to make the experiments is strictly
limited, the longest unbroken period being one hour twenty
minutes in the School Certificate form and the form below it.

It is impossible for the teacher to verify all results in a short
lesson, but it is good for pupils to have responsibility, and to feel
the recorded results must depend on their own unaided work. It
has been found that the fact that they were helping to build up
the school records does appeal to the girls' sense of responsibility.

An objection has been made that this experimental method
demands more time than is usually allotted. At Dulwich an
unusual amount of time has not been given to Botany. The ex-
periments on pollination, for example, were for many years done
by girls who had only one lesson of one hour per week for
Botany, and in earlier days still, by classes of forty girls who had
only forty minutes. The experiments could only be made on
fine days in the summer term, and only part of the time could
be given to the experimental work.

Great stress is laid on control experiments, the necessity for
which is readily appreciated by the girls, and arouses their
critical faculties.

The experimental method of studying Botany has been greatly

PREFACE vii

helped by the development of Botany Gardens. The gardens
have been made gradually in response to the needs of the work.
They have become, in many cases, out-of-door laboratories, and
the work indoors and out of doors is one. The gardening work
itself is voluntary and always has been, but there has never been
a lack of volunteers.

In the laboratory, in classes up to and including the School
Certificate examination class, the compound microscope is not
used, except in studying a green alga, such as Spirogyra, and the
minute structure of a leaf. Much can be seen with the aid of a
good hand-lens, for example, in a piece of wood. The structure
in sections of dicotyledonous stems, monocotyledonous stems,
lenticels, maize grains, and the mouth parts of insects mounted
whole, show well, viewed by a magnifying glass in a special
slide holder* Malpighi made his classical discoveries with a
simple microscope no better than a half-crown lens of the present
day. He was the first to observe the capillaries (1661), he made
the earliest anatomical study of an insect (1669), and he demon-
strated the nature of the tissues of many animals and plants.

Records.

The keeping of records goes on steadily year after year. It
was difficult to keep many in the early years (1896-1912) when
the gardens were being made and there was no grant, little
assistance, and the work had to be done in out-of-school hours.

This book deals with experimental and ecological work. For
want of space the accounts of many experiments have been
omitted. Other branches of the work, such as morphology and
classification, are not included.

With a few exceptions the work described is the work of the
pre-Matriculation or School Certificate classes, and not the more
advanced work.

H.M.I. Dr. Wager, F.R.S., on the occasion of his last visit of
inspection to the James Allen's Girls' School, urged me to write
a book giving an account of the work in Botany initiated and
developed by me at the school, and include in it records of
experiments.

My warmest thanks are due both to Professor V. H. Black-
man, F.R.S., Professor of Plant Physiology at the Imperial
College of Science, for reading Chapters I to VI (Experiments

viii PREFACE

in the Laboratory), and to Professor Tansley, F.R.S., Sherardian
Professor of Botany, Oxford, for reading Chapters VII to XIV
(the Botany Gardens), and for their most valuable suggestions.
Also to Professor Tansley for the kindly interest he has taken for
years in the Botany Gardens.

I am greatly indebted to Miss Talbot, B.Sc., second Botany
Mistress 1912 to 1916, and my successor from 1926 to 1931, the
last date up to which the selected records have been taken. Miss
Talbot has given constant help throughout the writing of this
book.

All the diagrams have been made by 'old girls'. Many more
would have liked to help if they had been easy of access. My
thanks are due to those who have made the diagrams, and to the
great number of 'old girls' without whose help the Botany
Gardens could not have been made or maintained.

LILIAN J. CLARKE.

3, BISHOP'S COURT,
EAST FINCHLEY,

N.2.

CONTENTS
EXPERIMENTS IN LABORATORY

CHAPTER I
SEEDS AND SEEDLINGS ..... i

Experiments to see if seeds will germinate (i) in oxygen, nitrogen,
carbon dioxide, (2) at various temperatures. Reserve substances in seeds.
Tests for starch, proteins, oils. Action of diastase on starch. Absorption
of water by roots, experiments to see if plants can absorb solids, path of
water in roots and stems. Growth of seedlings in light and absence of
light. Effect of brief light exposure on etiolated seedlings.

CHAPTER II
PHOTOSYNTHESIS ...... 8

Production of starch. Green leaves from 416 plants of different species
tested for starch. Summary of records of experiments. Many results
checked by microscopic examination of leaf sections by elder girls. Tests
for sugar when no starch found. Conditions necessary for production of
starch. Evolution of oxygen. Records of experiments.

CHAPTER III
FOOD OF PLANTS . . . . . .16

Constituent elements of plants found by analyses. Essential elements
determined by growth of plants in various culture solutions. Generations
of plants in culture solutions. Summary of thirty years' experience in
water-cultures.

CHAPTER IV

TRANSPIRATION . . . . . .22

Liquid tested. Results of experiments on 298 plants to see if pores are
present in leaves, and distribution of pores if present. Strips of epidermis
under microscope. Minute structure of leaf. Comparison of rates of
transpiration from upper and lower surfaces of leaves. Potometer.
Comparison of rates of absorption and transpiration. Weight of water
lost in transpiration. Rate of transpiration under varying conditions.

RESPIRATION ....... 28

Experiments to see what gas is given off, what gas is taken in. Comparison
of volumes. Production of heat. Records of experiments. Anaerobic
respiration.

4158

x CONTENTS

CHAPTER V

GROWTH IN PLANTS . . . . . - 35

Experiments showing distribution of growth in roots and stems. Graphs.
Measurement of growth in length.

DIRECTION OF GROWTH . . . . -39

Experiments showing influence of presence of water, light, and gravity.
Growth of plants on a clinostat. Perception of gravity in a root.

CHAPTER VI
THE SOIL ....... 48

Determination of percentages of (a) water lost when soil is air-driecl,
(b) water present in air-dried soil. Mechanical analysis of a soil. Sand
and clay compared as to the rate at which (i) water passes up, (2) air
passes through. Water capacities of soils. Determination of percentage
of humus in various soils. Factors influencing temperature of soils
(colour, aspect).

THE BOTANY GARDENS

CHAPTER VII
HISTORY AND ORGANIZATION . . . .55

Begun in 1896. No grant for fifteen years. Grant from Board of Educa-
tion in 1912. Out-of-school voluntary work in a day school. Organiza-
tion. Use of tools. Visitors from many countries. Subjects of theses in
Spain, France, Sweden. School Botany Gardens made elsewhere. Study
of animals. Biology gardens.

CHAPTER VIII
POLLINATION EXPERIMENTS . . . .60

Experiments (a) to find the function of pollen (records of 4,000 experi-
ments), (b) to see if self-pollination can take place in various plants (6,000
experiments). Experiments on pollination of primrose. Records of
insects seen visiting flowers.

CLIMBING PLANTS . . . . . .71

Plants in garden, in class-room, and in laboratory. Experiments showing
rates of revolution, influence of thickness of support, and angle of in-
clination of support. Effect of inversion, growth on a clinostat, and
absence of light, on twining stems.

CHAPTER IX
THE LANE ....... 75

Construction. Cost. Study of plants in spring, summer, winter. Tendril
climbers. Determination and comparison of degrees of sensitiveness
of tendrils. Influence of aspect on time of flowering of plants. Influence
of aspect on soil temperatures. Animal life in the Lane. Plants of the
J.A.G.S. Lane.

CONTENTS xi

CHAPTER X
THE PONDS ....... 82

(a) Large pond. Construction. Cost. Water supply. Drainage. Fresh-
water marshes.

() Smaller pond for little plants crowded out in larger pond. Con-
struction.

List of plants in J.A.G.S. ponds and marshes. Great vegetative reproduc-
tion. Plants to avoid.

CONDITIONS UNDER WHICH WATER PLANTS LIVE . 89

Comparison of maximum and minimum temperatures in pond and in
air above pond. Study of animal life in ponds.

CHAPTER XI
THE HEATH ....... 93

Construction. Soil from a Surrey heath. List of plants in J.A.G.S.
heath.

THE BOG ....... 96

Large one in heath. Construction. Peat from Lancashire. Cost. List
of plants in J.A.G.S. bogs.

CHAPTER XII
SAND DUNES ....... 99

Construction. Cost. Colonization of big sand dune by a sand-sedge
plant. Vegetative reproduction. List of plants in J.A.G.S. dunes.

SALT MARSHES . . . . . . 101

Soil obtained from two sources. Experiments to ascertain suitable
strength of salt solution to be poured on marshes. Quantity of salt
solution given in one year. Particulars of research work done by an 'old
girl' on J.A.G.S. salt marsh. Material for other research at present time.
List of plants in J.A.G.S. salt marshes.

PEBBLE BEACH . . . . . .104

Pebbles from Brighton. Cost. Imitation of nature in covering up plants
with pebbles, and in providing seaweed ('drift') for beach. List of plants
in J.A.G.S. pebble beach.

CHAPTER XIII
CORNFIELD . . . . . . .107

(a) Small and large, (b) Plots of wheat, barley, oats, rye. Weeds of the
cornfield.

MEADOW. Dominant grasses. List of plants . . .108

xii CONTENTS

CHALK BEDS. Construction. List of plants . . .no

THE WALL. Construction. List of plants . . . in

VARIATION . . . . . . .112

STRUGGLE FOR EXISTENCE . . . . .112

MENDELIAN EXPERIMENTS . . . . . 113

Actual results in F 2 generation compared with theoretical results.

SOIL EXPERIMENTS . . . . . .115

MANURIAL EXPERIMENTS . . . . .116

Recent experiments on mustard. Advice from Rothamsted Experimental
Station. Plots treated with complete artificial manure, manure lacking
phosphate, &c.

CHAPTER XIV
THE WOODS . . . . . . .119

Consideration of soil. Damp oakwood the type chosen. 783 oaks
(Qiiercus robur) planted. Competition of woodland plants and 'weeds'.
Age at which acorns were borne. Birds' nests. Thinning of trees. Plant
diseases. Changing conditions in the wood: (a) humus content, (b)
evaporating power of atmosphere, (c) light intensity. List of trees, shrubs,
and herbs in J.A.G.S. wood.

APPENDIX . . . . . . .132

INDEX . . . . . . . .137

NOTE

P. 115, F 2 Generation.
For Purple flowers read Coloured flowers

LIST OF ILLUSTRATIONS

1. The Ponds in Spring at J.A.G.S. . . . frontispiece

2. Growth of bean seedlings of same age in light and absence of light 6

3. Etiolated seedlings exposed to light for various periods . . 7

4. Starch print . . . . . . .10

5. Moll's Experiment. Part of leaf in air deprived of carbon dioxide 12

6. Fifteenth generation of pea plants grown in food solution

facing p. 1 6

7. Four generations of Aloe plants in food solution . 18

8. Cork for food solution jar . . . . .20

9. Surface view of stomates (magnified) . . . .24

10. Transverse section of a leaf (magnified) . . .24

1 1 . A Potometer . . . . . . .26

12. Experiment to compare rates of absorption and transpiration . 27

13. Apparatus for seeing if germinating seeds give off carbon dioxide 29

14. Apparatus for seeing if germinating seeds take in oxygen . 30

15. To compare the volume of gases taken in and given off during

respiration . . . . . . 31

1 6. Graph showing region of growth in radicle of pea . . 36

17. Graph showing region of growth in hypocotyl of sunflower . 37

1 8. An Auxanometer . . . . . 38

1 9. Stem of Geranium growing through hole in door towards the light 4 1

20. Influence of light on direction of growth of hypocotyls . .41

2 1 . A Clinostat . . . . . . .44

22. Influence of gravity on direction of growth of stem of bean seedling 45

23. Influence of gravity on direction of growth of hypocotyl of

sunflower . . . . . . .46

24. Geranium plant turned upside down . . . .47

25. Rise of water in sand and clay . . . . -50

26. Graph representing rise of water in sand and clay . 51

27. Bracket for tools . . . . . -57

28. Pollination experiments in Botany Gardens . . facing p. 62

29. Transect of hedge . . . . . .76

30. Transect of pond . . . . . .84

31. Big pond and back of lane .... facing p. 86

32. Colonization of sand dune by a single sand-sedge plant . 98

33. Pebble beach with distant view of wood . . 104

34. The dell and atmometer . . . 128

35. Undergrowth in damp oakwood . . . 130

FOREWORD

ELIAN CLARKE was a really great pioneer in the field
of school education. Her thoroughly sound fundamental
ideas, her extremely clear and honest mind, her keen en-
thusiasm, and her indomitable energy and perseverance com-
bined to give her the great success she attained. She trained at
least two women who have become distinguished investigators,
and there must be scores of others on whom her influence and
their experience at Dulwich have left a lifelong mark. The
keynotes of her work are common property that her girls should
do things for themselves, that they should set up control experi-
ments wherever practicable, that their observations should be
exact and properly recorded, and that they should always keep
clear the distinction between fact and inference. But it has been
given to few teachers to carry these universally accepted precepts
into such continuous and effective practice and over so wide a field
of the subject.

She met with many difficulties, and for years carried on an up-
hill fight for money and opportunity for her work. But nothing
daunted or discouraged her, and eventually she gained the warm
sympathy and active assistance of headmistress, school gover-
nors, Board of Education, and school inspectors alike, as well as
of many outside people in a position to help. She often came to
me for advice, and I was frequently amazed at the boldness of her
schemes for new extensions of the work and rather sceptical as to
their practicability. Nevertheless, she very rarely failed to carry
them to a successful issue. If she made mistakes, she never spared
ingenuity or trouble till they were satisfactorily corrected as far
as possible. This was particularly true of her creation of a whole
series of 'ecological habitats' lane, pond, bog, sand dune, shingle
beach, salt marsh, oakwood in which could be grown the native
plants that naturally inhabit them. As an ecologist I was naturally
always urging her to 'let things alone' as much as possible, once
a new distinctive habitat was established; but this she could
rarely do at all fully, as was natural enough when we remember
the largely artificial conditions that have to be maintained in
order to get the plants to grow at all and to keep down weeds.
Even so, a considerable number of really valuable ecological

xvi FOREWORD

observations were accumulated, and there would have been
many more if she could have had another ten years at the work.
And this quite apart from the educational value to the girls of
these pioneer efforts.

In this little book will be found a full record of Miss Clarke's
work her ideas, her plans, her methods, her difficulties, and her
successes. It is a story of absorbing interest, and the book is
packed with useful practical records and suggestions of all kinds.
Miss Clarke was not a practised writer of text-books and she does
not always present her material in the way that would be most
useful to contemporary teachers who wish to follow her example.
Some may regret that she did not write a regular practical hand-
book for school laboratory and garden work, rather than a record
of her own work at Dulwich. But the material is all there and can
be extracted and used to great advantage. Laboratory work in
plant physiology, which was quite a novelty in secondary schools
at the end of last century when Miss Clarke was appointed to her
post at the James Allen's Girls' School, has long become a regular
part of the curriculum in the better schools and has been con-
siderably developed and perfected, so that some of the author's
descriptions of elementary experiments may now seem redundant.
But it is all part of her story, and it is a story which is not only
inspiring as an example but instructive in numberless details.

I most cordially commend the book to all practical teachers
of biology in schools both girls' and boys' and to every one
interested in school science.

A. G. TANSLEY
OXFORD
April 1935.

EXPERIMENTS IN LABORATORY

SEEDS AND SEEDLINGS

Conditions necessary for germination. Tests for reserve substances in seeds.
Absorption of water. Growth of seedlings in light and absence of light.

IT has been found that the study of seeds and seedlings furnishes
a good beginning for work in plant physiology. It leads to the
consideration of storage of food reserves, root absorption, trans-
port of raw material, influence of light and gravity on direction
of growth, and other subjects of great importance in the life of
the plant.

The seed under favourable conditions germinates and forms
a seedling. What are the conditions necessary for germination?

i. Seeds germinate in the air, a mixture of gases of which
nitrogen and oxygen form the major part. Will they germinate
in nitrogen alone? in oxygen alone? Ordinary air contains
about three parts per 10,000 of carbon dioxide. Will seeds
germinate in carbon dioxide?

At the James Allen's Girls' School it has been found con-
venient to use respiration retorts ('respiroscopes') 1 for these ex-
periments. Some pea seeds are placed in the bulb end, the retort
is filled with water, and a gas is passed into the retort under
water, and is allowed to displace all the water except a very
small quantity. A well-fitting india-rubber cork is placed in the
open end under water; the retort is then taken out and placed
with the corked end in a beaker containing water, as an extra
precaution to prevent entrance of air. If time permits, this
making of the gases and filling of the retorts can be done by the
girls themselves, who, at this stage, have a sufficient knowledge
of the gases of the atmosphere. In some years the work has been
done by the girls in their chemistry lessons. Each gas under
consideration is passed into several retorts, and each retort con-
tains several seeds, in order that conclusions may not be drawn
from a few results. Some control experiments are made with

1 A slightly modified form of chemical retorts.
4158 B

2 EXPERIMENTS IN LABORATORY

seeds from the same packet, left with a little water in the air of

other retorts, which are also corked.

After the experiments have been left for a time, it is seen quite
clearly that the seeds have germinated in the control experi-
ments and in oxygen, but not in nitrogen or carbon dioxide.

2. Will seeds germinate at all temperatures? It would not
be possible to find every temperature at which various seeds
germinate, but it is easy to take two extreme temperatures,
approximately o C. and 100 C., and see if seeds will germinate
at those temperatures. It is well to take seeds, such as mustard
and cress, that germinate quickly, so that in the one case much
ice need not be used, and in the other the water-oven need not
be heated for a long period. The seeds are placed on damp
sawdust in three crucibles. Ice is put in one crucible, which is
surrounded by ice in a basin and put in the coldest place
available; another crucible is put in a water-oven; the third is
left in the laboratory as a control experiment. Equal quantities
of water are given to all. When the seeds in the control experi-
ment germinate, those which have been surrounded by ice have
not germinated nor those which have been in the water-oven.

If the crucibles are then left in the laboratory at a normal
temperature, the seeds which have been at a very low tempera-
ture germinate, but not those which have been in a water-oven
at about 100 C.

3. It is known to all that water in some form is necessary for
the germination of seeds, and pupils can devise their own experi-
ments, or bring forward facts to show that this is the case.

Summary. It is therefore found that the germination of seeds
depends on (i) the presence of oxygen (as far as experiments
have been made), (2) a certain amount of warmth, (3) the
presence of water.

Light and germination. Recently it has been shown that a
number of seeds, as those of the great hairy willow-herb, purple
loosestrife, curled dock, and celery-leaved crowfoot, under
normal temperature conditions, can only germinate in the light,
or have their germination promoted by illumination. A small

SEEDS AND SEEDLINGS 3

number, such as Phacelia tenacetifolia, can germinate only in the
dark. Temperature, however, seems to play an important part.
Those seeds which under normal temperatures only germinate
in the light may do so in the dark at a high temperature, and
those which normally only germinate in the dark may germinate
in the light at a low temperature. 1

Experiments have been made at J.A.G.S. which showed the
advantage of the presence of light on the germination of the
seeds of the great hairy willow-herb, and the disadvantage of
light on the germination of seeds of Phacelia tenacetifolia.

Reserve substances in seeds. Many seeds, such as pea, bean,
and sunflower, germinate and develop into fairly large seedlings,
if they are placed in damp sawdust which contains no nourish-
ment. Examination of the seeds of these plants shows that they
contain reserve food material. To determine the nature of
these reserves pupils must know the tests for starch, proteins,
and oil. Sometimes the members of the class have learnt these
tests in their chemistry class. If they have not, the various
reactions must be shown in the botany class.

1 . Iodine solution (see appendix) is poured on pieces of starch,
and a dark blue, almost black, coloration is seen.

2 . A little caustic potash is added to some protein, such as white
of egg, in a test-tube, enough to cover it, and one drop of copper
sulphate added. A mauve colour is seen after a short time.

3. A little oil is placed on blotting-paper, and a greasy stain
is produced which is not removed when the paper is dried.

(If seeds are being tested for oil they can be crushed between
blotting-paper after the outer coats have been removed, or
slices can be cut and heated at a gentle heat in an oven on
blotting-paper.)

Summary of results. Scarlet runner seeds, broad bean seeds,
and pea seeds contain starch in their cotyledons, maize and
wheat grains in the endosperm; castor oil seeds, maize grains,
and wheat grains contain proteins in the endosperm, sunflower,
pea, and bean in the cotyledons; castor oil, sunflower, mustard,
and Brazil nut seeds contain oil. (For list of parts of plants
other than seeds tested for starch, sugars, proteins, see appendix.)

1 Skene, The Biology of Flowering Plants, 1924.

4 EXPERIMENTS IN LABORATORY

Action of diastase on starch. When the seed germinates
active growth takes place and food is needed. Starch is insoluble
and indiffusible, therefore, when the reserve food is starch, it
must be changed into a soluble substance before it can travel
to the parts where it is needed, such as the growing-points of
roots and stems. This change is effected by diastase, which is
present in germinating starchy seeds, and can be obtained from
germinating barley grain, for example.

In order to see the action of diastase on starch a thin starch
paste is made (2 grams starch mixed with 20 c.c. cold water
and 200 c.c. boiling water added). Some of the starch paste is
put into a test-tube A, and some into a test-tube B. A small
quantity of diastase is added to the paste in B, and both test-
tubes are placed in a water-bath, the temperature of which is
about 50 C.

Contents of test-tube A divided into two and tested.

1 . Iodine solution gives a dark blue coloration.

2. Heated with Fehling's solution no reddish-brown pre-
cipitate seen.

Contents of test-tube B divided into two and tested.

1. Iodine solution gives no blue coloration.

2. Heated with Fehling's solution a reddish-brown pre-
cipitate is seen.

The starch in B has been changed into sugar by the action of
diastase.

Absorption of water by the root. Pea and bean seedlings
are placed with the lower parts of the roots in water coloured
with eosin. (Red ink can be used.) After a day or two the roots
are cut across at different places above the level of the water,
and it is seen that the coloured water has been absorbed and
has travelled up the root. On placing other seedlings, similar
to those above, with the lower parts of the roots in water con-
taining carmine particles (which give a red colour to the water,
but which, unlike eosin, are insoluble in it) it is found on cutting
the roots across at various levels that the carmine has not entered.
Roots do not absorb solids. The same result can be seen very
clearly by placing the roots of one plant of narcissus with white
flowers in eosin solution, and the roots of another in water
coloured with carmine.

SEEDS AND SEEDLINGS 5

Young plants with a good tap-root, such as hedge parsley,

also show absorption of coloured water well and are easier for

the girls to cut than seedlings.

The above experiments in which the roots of seedlings and

plants were in eosin solution showed that the water travelled

through the central part of the root the stele.

Path of water in the stem. The path of water coloured by
eosin can be seen in the stems of seedlings but not so easily as in
older stems.

Laurel twigs are placed in bottles containing eosin solution.
At the next lesson it is noticed that the leaves are distinctly
coloured, especially the veins, showing that water has travelled
up the stem to the leaves. When members of the class cut across
the stem above the part which had been immersed in eosin, it
appears to be the wood which is coloured. In order to ascertain
if this is the case, without using a microscope, other twigs of
laurel are taken, and a ring of tissue about J inch in depth is
removed from the stem, the cut penetrating as far as the wood.
The twigs are then placed in eosin solution with the cut part
above the level of liquid, and the leaves become coloured as in
the first experiment, the wood in the stem also, but not the pith.

Water ascends through the wood (xylem) of a stem to the
leaves.

Transverse sections of the leaves cut by older girls show that
the water has passed through the upper part of the vascular
bundle the wood.

Seedlings in light and absence of light. Some runner bean
seeds of approximately the same size are put in damp sawdust
in a number of pots, one in each pot. Some pots are put in a
dark cupboard, or preferably a dark-room, and some are kept
in the laboratory near a window. The same quantity of water
is given at the same time to both sets of seeds, and, when the
seeds germinate, to the seedlings. The differences in the
development of the seedlings in the light and in the dark are
most marked, as shown in a copy of a photograph (Fig. 2).

The seedlings grown in the dark are characterized by:

1. Great length of internodes.

2. Small dimensions of leaf.

6 EXPERIMENTS IN LABORATORY

3. Weakness of stem.

4. Absence of green colour.

In making the above experiment it is well not to bring the
seedlings from the cupboard or dark-room into ordinary light
when examining them or watering them, but to use a ruby light.

FIG. 2. Growth of Bean seedlings of same age in
light and absence of light.

Exposure of etiolated plants to light for short periods.

It has been shown that exposing etiolated seedlings to the light
for even one minute a day makes a difference in their develop-
ment. 1

Experiments in light-proof boxes have been carried out at
J.A.G.S. by members of the post-matriculation class. It was
found that etiolated seedlings of pea exposed to light on con-
secutive days for one minute showed (i) shorter internodes,
(2) signs of lateral leaf development, and (3) a slightly less
pronounced plumular hook, than those kept always in the dark.

1 Priestley, 'Light and Growth', New Phytologist, 1925.

SEEDS AND SEEDLINGS 7

Etiolated seedlings were also exposed to light for other lengths
of time, namely 30 minutes, and 60 minutes per day, and the

mm light-
per day

1 mm hghr
per day

30 mins lighf
per day

60 mins. l
per day

FIG. 3. Etiolated seedlings exposed to light for various periods.

Note variation in: (i) length of internode, (2) development of lateral
leaf, (3) plumular hook.

effects noted. Those exposed for 60 minutes a day showed a
faint green colour.

Additional experiments with seeds and seedlings are described
in Chapters III, IV, and V.

II

PHOTOSYNTHESIS

STARCH has been found in the reserve organs of many plants.
Experiments are made to see if leaves contain starch, and, if
so, under what conditions. The girls, while in the laboratory,
decide which leaves in the garden, not already tested, they will
examine for starch. They pick the leaves, place them in boiling
water for ten minutes, and leave them in methylated spirit until
the next lesson. If it is wished to decolorize the leaves quickly,
after being in boiling water they are placed in a small beaker
containing methylated spirit and the beaker is suspended in a
larger beaker containing boiling water. (Methylated spirit is
highly inflammable.) The decolorized leaves are washed,
placed on white dishes, and iodine solution is poured on them.
The results of the experiments of all the members of a class are
recorded, and a list made of the green leaves in which starch
has been found, and of those in which no blue coloration was
seen. Then, and not until then, reference is made to the results
of experiments of former years, and in this way, generalizations
with regard to the presence or absence of starch in leaves of
dicotyledons and monocotyledons are being based on a large
and increasing number of results.

Summary of records made in twelve years.

I. Decolorized leaves treated with iodine. Macroscopic
method.

(a) The leaves of all dicotyledons picked in the light have
been found to contain starch. 388 species.

(b) The leaves of 4 monocotyledons picked in the light, and
treated as above, showed a decided blue coloration. Arrow-
head, black bryony, Elodea, wheat.

(c) The leaves of 24 monocotyledons picked in the light, and
treated as above, showed no blue coloration.

Bluebell Garlic

Cotton Grass Grape Hyacinth

Daffodil Grass, Fescue

Day Lily Meadow

PHOTOSYNTHESIS 9

Grass, Purple Moor Onion (very young leaves not taken)

Sand Lyme Pondweed, Floating

,, Water Reed, Common

Iris Sand Sedge

Lily, Madonna Snowdrop

Lily-of-the- Valley Solomon's Seal

Montbretia Tulip

Narcissus Woodrush

II. Microscopic method. Sections of some of the above
leaves were cut, treated with iodine, and examined under the
microscope by elder girls specializing in science. Of the leaves
of 24 monocotyledons in which no starch was found by the
macroscopic method, no starch was seen in the sections in the
mesophyll, or inner tissue of the leaf, but in several starch was
found in the guard-cells of the stomates (lily-of-the-valley, iris,
snowdrop) .

Possible sources of error. In noting the results of these experi-
ments on leaves of monocotyledons it must be remembered that
the best time for testing the main body of the leaf (the mesophyll)
for starch is the late afternoon, and the best time for starch in
the guard-cells is early in the morning after dark, and that no
botany lesson comes at either of the above times. Also, it has
been suggested that in some monocotyledons the capacity for
producing starch diminishes as the leaf grows older. In wheat
it has been found that in June starch was present in the leaf
blades, in July it was only visible at the junction of blade and
sheath, and in August no starch was found in leaves or stem
though the latter was green. 1

Leaves tested for sugar. The following monocotyledonous
leaves which showed no starch in their mesophyll were tested
for sugar, and glucose (grape sugar) was found: bluebell,
meadow grass, iris, lily-of-the-valley, common reed, Solomon's
seal.

General statement. Of the dicotyledonous plants 100 per
cent, showed dark blue coloration in the leaves with the iodine
test; of the monocotyledons only 14 per cent, (excluding those
having starch only in guard-cells) ; of the total number of species
tested 93 8 per cent.

1 Parkin, Philosophical Transactions. Royal Society, B, vol. 191, 1899.
4158 G

io EXPERIMENTS IN LABORATORY

In the green leaves of most plants starch is found. What
conditions are necessary for its production?

i. Is starch found in green leaves in the absence of light?

Plants, such as fuchsia and geranium, which had been shown
in former experiments to have starch in their leaves, are put in
the dark, preferably in an airy place, until by means of the

iodine test it is seen that
no starch is present in the
leaves. Some of the plants
are left in the dark-room,
or a cupboard, and some
are put in a good light
in the garden, as control
experiments. After a time
leaves are picked from
both sets of plants, de-
colorized, and treated
with iodine. Hundreds of
experiments have shown
that if starch-free leaves
are left in the dark no
starch is afterwards found
in them, but that starch
is present in the leaves of
FIG. 4. Starch print. the control experiments in

the light.
Starch prints.

(a) Tin foil, or black paper, in which a stencil has been cut,
is bound loosely on the upper surface of a starch-free leaf, still
attached to the plant, so that that part will receive no light, but
air will not be excluded. (Tin foil is good to use as it has many
tiny holes, and therefore does not cut off air from the leaf.)
Sometimes the word STARCH is cut, sometimes initials, often
other devices, the stencil of a cat being popular with one set
of girls.

The plants arc put in a good light, and after some hours the
leaves are picked, decolorized, and treated with iodine. The
word STARCH, or initials, or the outline of a cat, appears in dark
blue on the leaf, while the rest of the leaf is yellowish.

PHOTOSYNTHESIS 11

Starch is only present in the part which had been exposed to
the light.

(b) Small's leaf clasps have also been used to obtain starch
prints.

2. Is starch found in green leaves in the absence of carbon
dioxide? It can be shown that starch contains carbon by heat-
ing it. The plant is surrounded by air which contains normally
about 3 parts per 10,000 of carbon dioxide. Does the plant
obtain carbon from this carbon dioxide?

At one time in order to ascertain if this was the case a sub-
merged water plant (Elodea), which had no starch in its leaves,
was placed in water which had been boiled and contained no
carbon dioxide. The control experiment had unboiled water.
Both experiments were placed in the light, and later starch was
found in the leaves of the control experiment but not in the
other.

But it was felt that changes, other than expelling the carbon
dioxide, may be made by boiling the water, so Moll's experi-
ment (see Fig. 5) has been used for many years.

A fuchsia, or other suitable plant, is placed in the dark, until
its leaves are free from starch, and then the tip of a leaf, while
still attached to the plant, is passed into the neck of a wide-
mouthed bottle in which is a little caustic potash or lime water.
A cork, which has been cut into halves, is fitted into the neck
of the bottle, so that the tip of the leaf is in air free from carbon
dioxide, the middle part between the cut halves of the cork, and
the base outside the cork. The bottle is supported by a clamp
and the apparatus is left in a good light. At the next lesson the
leaf is picked, decolorized, and treated with iodine. Hundreds
of experiments have shown the same results. The part of the
leaf that had been outside the cork contains starch, but the
parts that had been covered by the cork and in the air devoid
of carbon dioxide contain no starch.

(A useful feature of the experiment is that the leaves can be
left in methylated spirit, and at any time with the aid of iodine
solution the starch-free part of the leaf can be shown.)

Carbon dioxide is taken in by the leaf. Is any gas given off
during the process of starch formation? It is better to use water
plants, as it is easier to collect any gases that may be given off.

12

EXPERIMENTS IN LABORATORY

Elodea from the pond is used. It is not allowed to be exposed
to the air but is transferred from the pond into a basin contain-
ing water. It is kept in the dark until it is starch-free (it often
takes several days for starch to disappear from a water plant),
and then is put into deep beakers containing water.

P-KIMBER

FIG. 5. Moll's Experiment. Part of leaf in air
deprived of carbon dioxide.

A large funnel with the stem cut off is put over the Elodeti in
each beaker. A 'boiling-tube' full of water is inverted over the
ends of the Elodea shoots under the funnel and the beaker placed
in a good light. Bubbles arise from the Elodea and a gas collects
in the tube, and is tested with a glowing splinter. The splinter
is rekindled, is blown out, and rekindled again and again.

Every two girls in a large class set up this experiment each
year, and in the course of a few years records of many experi-
ments have been obtained. A record of 59 experiments shows
that the splinters were rekindled 213 times, an average of more

PHOTOSYNTHESIS 13

than 3. Sometimes the splinter is rekindled 6 or 7 times. The
gas is evidently rich in oxygen. No oxygen is evolved in the
control experiment in which there is no Elodea. (The iodine
test showed the presence of starch in the Elodea leaves.)

The above experiment showing that a green plant in the
presence of light and carbon dioxide gives off oxygen, reminds
us of the classical experiment of Priestley, the discoverer of
oxygen, the bicentenary of whose birth has recently been
celebrated (1933). He recorded: 'On the iyth of August, 1771,
I put a sprig of mint into a quantity of air in which a wax
candle had burned out and found that on the 27th of the same
month another candle burned perfectly well in it. 5

Experiments, similar to the above (Elodea under a funnel in
a beaker), are set up in the dark. No oxygen is given off, and no
starch is found in the Elodea.

Priestley also discovered that green colouring matter and
sunlight were necessary for the giving off of the gas (afterwards
called oxygen) by the plant.

3. Is oxygen given off by green plants at low temperatures ?

Ice is put in the water in some beakers containing starch-free
Elodea under a funnel, and renewed inside and outside the
funnels, until in the control experiments, where there is no ice,
a gas, which can again be shown to be oxygen, has collected
in the tubes. No gas collects when the temperature of the water
is very low, nor can starch be found in the Elodea. Both sets of
experiments are kept in a well-lighted place.

4. Is starch found in leaves in the absence of chlorophyll?

A simple way of answering this question is to use variegated
leaves. The leaves of several plants have been used variegated
maple, splashed dead-nettle, variegated pelargonium, and varie-
gated mint, but mint has been found to give the best results. On
account of this, many groups of variegated mint have been
grown in different parts of the garden, so that during a lesson,
a number of girls can go out, pick the leaves, and return to the
laboratory in a short time. The leaves are drawn very carefully,
the parts which are green in the leaf being shaded in the drawing;
the leaves are then decolorized and tested with iodine. On
reference to the drawings it is seen that the part which has

i 4 EXPERIMENTS IN LABORATORY

become dark blue corresponds to the part which was green,

and the part where no starch has been produced to the white

part.

Summary. It has, therefore, been shown, not in one experi-
ment only in each case, but in hundreds, that for the production
of starch the following are necessary: light, presence of carbon
dioxide, warmth, and chlorophyll.

Is starch made in green leaves ? A fuchsia plant, or geranium
plant (in the leaves of which starch had previously been found) ,
is put in a dark-room, or cupboard, until the leaves are found
free from starch. Several leaves arc then picked and put with
their stalks in water, some in the light, some in the dark. After
a day or two they are all decolorized and tested for starch. It
is found that starch has been made by the green leaves in the
light.

Disappearance of starch. Starch formed in green leaves in
the light disappears in the dark. Does it disappear more quickly
when the leaf is on the plant, or when it is detached ? A plant
that had been in the light and contained starch in its leaves is
put in the dark room, several leaves are picked from it and left
with their petioles in water also in the dark. After 16 hours
some more leaves are picked from the plant, and both sets of
detached leaves decolorized and treated with iodine. A dark
blue colour is seen in the first set of leaves that had been
detached, but none in the second. Starch disappears more
rapidly from leaves attached to a plant than from those detached.

Starch is insoluble, but as was shown in Chapter I, it can be
changed into sugar by diastase. Diastase is present in leaves
and can be obtained from them.

Photosynthesis. Starch is a carbohydrate. It consists of
carbon, hydrogen, and oxygen, the proportion of hydrogen to
oxygen being the same as exists in water two parts of hydrogen
to one of oxygen. It has been shown how the plant obtains the
carbon. How does it obtain the necessary hydrogen and
oxygen? Water taken in by the root-hairs ascends through the
root and stem to the leaves. The green plant is able by means

PHOTOSYNTHESIS 15

of the energy absorbed from the sun by chlorophyll to make
sugar and starch from the carbon dioxide taken in by the
leaves, and the water taken in by the root-hairs. The whole
process of taking in carbon dioxide, building up of carbohydrates,
and evolution of oxygen is called photosynthesis. It is a most
important process as the life of the world depends on it. No
animals could live if plants did not carry on this process.

'Animals are in the long run always dependent on green plants, they are,
one might almost say, parasitic upon plants. Green plants, by the same
token, are parasitic upon the sun, they live by stealing energy from his
rays.' HALDANE AND HUXLEY.

Ill

FOOD OF PLANTS

Constituent elements of plants found by analyses. Essential elements deter-
mined. Plants in culture solutions. Summary of thirty years' experience
in water cultures.

E order to find out what elements are essential as food
.material to the life of the plant the first step is to ascertain of
what elements plants consist. If certain elements are never, or
seldom, present, they cannot be necessary. Plants, or parts of
plants, are heated in a water-oven to a temperature of about
1 00 C. during which process water is given off (in this way the
percentage of water in various plants can be found see appen-
dix), and then the dried plants are strongly heated until an ash
is produced, and the relation of the weight of the ash to the
original weight of the plant can be found (see appendix) .

Even if the pupils have only an elementary knowledge of
chemistry they can discover while the plants are being strongly
heated that carbon dioxide and ammonia are given off. The
ash must be analysed by others. But in some classes the pupils
will be able to discover for themselves that the ash contains
sodium, potassium, a sulphate, and a phosphate (see appendix),
so that they know that the following elements are present:
hydrogen, oxygen, carbon, nitrogen, sodium, potassium, sulphur,
phosphorus. It is usually beyond the power of girls at this stage
to analyse the ash completely. In some years it has been given
to senior girls, who are specializing in chemistry, and, failing
that, analyses, made by an expert, of the ash of various plants
have been used. Analyses showed that the metals potassium,
calcium, magnesium, sodium, and iron were present in the
form of sulphates, phosphates, chlorides, and silicates.

It has therefore been shown that thirteen elements are con-
stantly present in plants: hydrogen, oxygen, carbon, nitrogen,
sodium, potassium, sulphur, phosphorus, calcium, magnesium,
iron, chlorine, silicon.

In order to find out which of these elements are absolutely
necessary, numbers of plants have been grown in food solutions
(culture solutions) of varying constituents. If it had not been

FIG. 6. Pea plants. Fifteenth Generation in Food Solution
The above plants were grown from seeds produced on a single plant
the previous year. Two plants were grown from seeds of same pod

FOOD OF PLANTS 17

ascertained first which elements are constantly present in plants,
it would have been an endless task to find out by means of water-
cultures which of the ninety-two elements are essential to the
life of the plant.

The composition of the solution that has been used for
thirty-six years at J.A.G.S. is as follows:

Sachs* Solution (normal solution)

Distilled water . . . . . i litre

Potassium nitrate ...... i-ogm.

Sodium chloride . . . . . 0-5 ,,

Magnesium sulphate . . . . 0-5 ,,

Calcium sulphate . . . . . 0-5

Calcium phosphate . . . . 0-5

Ferric chloride . . . . . .a trace.

The above solution has been found most satisfactory. It seems
to suit all the plants that have been tried at Dulwich with the
exception of beech, and the absence of mycorrhiza in the beech
seedling may explain the failure. Schoolgirls are not, as a rule,
extremely careful, nor have they much time for these water-
culture experiments, but for a period of six years there was not
one case of a plant dying in normal food solution, unless it had
received some injury before it was put in the solution. Many
hundreds of plants have thrived in it, and the following list
will give some idea of the variety grown: almond, aloe, birch,
bramble, buckwheat, currant, edible chestnut, elder, false
acacia, gorse, hawthorn, hazel, holly, horse-chestnut, lupin,
maize, oak, orange, pea, peach, poplar, sunflower, sycamore,
Tradescantia, willow. 1

One year there were seventy perennials in food solution in
the laboratory. It is fascinating to watch the buds opening in
the spring, and to note the branching, and the nature of the
bud-scales (stipules in oak, leaf bases in sycamore and horse-
chestnut) . The development of buds can often be seen better
in these miniature trees than in the trees out of doors.

Seventeen generations of pea plants have been reared in the
above food solution, and have been of intense interest to the
girls. The late Francis Darwin when he saw the fourth genera-
tion of these plants thought they would degenerate, but they

1 All the plants were grown from seed except aloe, poplar, willow, and
Tradescantia.

4158 D

1 8 EXPERIMENTS IN LABORATORY

did not do so. In fact the plants of the seventeenth generation
were much finer and bore more fruits and larger fruits than the
earliest plants, but we draw no inference from this, as in fairness
it ought to be remembered that we became more skilled in
looking after the water-cultures, and also the conditions became
better.

A piece of aloe stem that had been left in water was found to
have developed roots, and was put in food solution. It has
lived more than sixteen years, is still living, and is almost
embarrassingly big. It has given rise by vegetative reproduction
to small plants which have been detached and grown in food
solution, and these in their turn have had descendants and
there are now in the laboratory four generations of aloes that
have never been in soil.

By leaving out one element at a time in a series of culture
solutions it has been possible for the girls to find out which of
the elements constantly present in the plant are essential to the
plant as food material. For example, potassium has been
omitted by substituting sodium nitrate for potassium nitrate,
nitrogen by substituting potassium sulphate for potassium
nitrate, 1 magnesium by omitting magnesium sulphate, sulphur
by leaving out magnesium sulphate and calcium sulphate and
using magnesium chloride, phosphorus by leaving out calcium
phosphate, iron by leaving out ferric chloride, and so on. It is
hardly necessary to say that many plants have been grown in
each of the abnormal solutions. In this way it has been proved
that potassium, nitrogen, magnesium, calcium, sulphur, phos-
phorus, and iron are necessary to the life of the plant. Other
experiments described in Chapter II have shown that carbon is
necessary, and that green plants obtain carbon from the carbon
dioxide of the air. Of the thirteen elements constantly found in
plants ten have been found to be essential: carbon, hydrogen,
oxygen, nitrogen, sulphur, phosphorus, calcium, magnesium,
potassium, and iron. Recent research work at Rothamsted has
shown that boron is also necessary for some plants.

Numbers of seedlings placed in distilled water have not lived,
but when choosing seedlings for these experiments care must
be taken to remove the store of food in the cotyledons or else-

1 Plants in culture solutions lacking nitrogen died, although they were sur-
rounded by the free nitrogen of the air.

FIG. 7. Four Generations of Aloe plants in Food Solution

FOOD OF PLANTS 19

where. At J.A.G.S. a pea seedling with cotyledons attached
was put in distilled water. True, it became a feeble plant,
comparing very unfavourably with pea seedlings in normal
culture solution, but it produced a flower and finally a fruit.
In making experiments to see what elements are essential it is
also necessary to see that any food reserve material is removed,
as otherwise the seedlings have a source of food apart from the
culture solution.

The equipment and conditions for the above water-culture
experiments were certainly not favourable at first. In very
early days the girls had only a hanging pair of scales, price two
shillings and sixpence, and a number of jam and pickle-jars.
For years the same small room was used for chemistry and
botany lessons, and the water-culture plants had to be moved
off the benches at many chemistry lessons, but still were in the
midst of fumes. In spite of these drawbacks the plants thrived.
Now they are in a large well-lighted botany laboratory which
possesses many balances. It is well to have good conditions and
good apparatus for experimental work, but it is a pity to wait
for these, and not to see what can be done in spite of difficulties.
As has been well said: 'To make the most of simple means is
an education in itself.'

It is interesting to note that from the experience gained at
school in growing plants in food solutions a former pupil, Dr.
Winifred Brenchley, when appointed on the staff of Rothams ted
Experimental Station, was able to begin at once that long series
of experiments that have been so valuable to farmers and
others. At first Dr. Brenchley at Rothamsted used a food solu-
tion of the same composition as she had used at school, but after
a time substituted 0^5 gm. potassium di-hydrogen phosphate
for O'5 gm. calcium phosphate. A weaker solution was subse-
quently used for some plants such as peas.

METHOD OF PROCEDURE AT DULWIGH

Gas-jars holding about one litre are used for the smaller plants,
and elaborate precautions in preparing the jars advised by some
writers have not been taken. It would have been impossible in
the short time at the girls' disposal, and with numbers of girls
working at the same time, to carry out all the precautions
advised.

20 EXPERIMENTS IN LABORATORY

At Dulwich the solution is boiled before it is used, but at
Rothamsted the water is never boiled. It is well, if it can be
arranged, not to use water that has been distilled in a copper
still. It has been shown that copper compounds usually act as
poisons to the higher plants. A concentration of i in 1,000,000
of copper sulphate in distilled water stops all growth in barley,
but if nutrient salts arc present a strength of i in 250,000 does

not prevent growth though the re-
tarding action is very considerable. 1
A flat cork (shive) is fitted to the
jar, and in the middle of the cork a
hole is bored, then a wedge is cut out
on one side of the cork, and a small
hole bored at the other side. Not
only seedlings and young plants are
grown in these jars, but plants which
live for years, develop bigroot-systems,
and have big stems, and it is con-
venient to be able to take them out easily from the cork when
the solutions or corks are changed, or the roots need washing.
Seeds are sown in clean sawdust which has been sterilized
and moistened with distilled water. When the seedlings are a
convenient size they are put in the solution in the jars. After
the stem of the plant has been placed in the centre of the cork,
cotton-wool is packed round it, and is also put in the gap in the
cork. For some years asbestos wool was used, but cotton-wool
has been found to be quite satisfactory.

The disease in seedlings called 'Damping off' is a common
cause of failure in water-culture experiments elsewhere.

Darwin and Acton stated that out of fifty-six unsuccessful
experiments, where plants died within three weeks, more than
thirty were attacked in this way. 2 Great care has been taken at
Dulwich that the cotton- wool should not project below the
lower surface of the cork, and that neither the cotton-wool nor
the lower surface of the cork should become damp. The level
of the solution in the jars is usually not less than f inch from the
lower surface of the cork, so that when the jar is moved the
solution may not wet the cotton-wool or cork.

1 Inorganic Plant Poisons and Stimulants, Brenchley, 1914.

2 Physiology of Plants , Darwin and Acton, 1909.

FOOD OF PLANTS 21

A glass tube is put through the second hole in the cork, the
end going nearly to the bottom of the jar. When the stem of the
plant is in position in the cork and surrounded by cotton-wool,
and the cork is in the jar, black paper is tied round the jar in
order that green algae may not develop. The black paper is
always removed when the jar is moved, and the level of the
solution watched to see if the cotton-wool or cork become wet.
No air is forced into the solution. Some must enter through the
loosely packed cotton-wool in the gap, and through the glass
tube which dips into the solution, but this tube is introduced
mainly on account of its usefulness as a support to the plant.

Frequent change of solution by the girls has not been possible
in the limited time at their disposal, only a small part of which
can be given to the water-culture experiments, as there are many
experiments to be made in other branches of botanical work.
Also there are the long holidays, and sometimes no new solution
is given for eight weeks. It would not be possible to change the
solutions as often as some writers recommend. From the records
kept of some of the perennial plants it appears that one plant
during 16 years had new solution 127 times, on an average
about 8 times a year, another plant during 1 1 years had new
solution 90 times, another during 4 years 31 times, and another
during 3 years 23 times.

These water-culture experiments have been a great source
of interest to the girls, have afforded a good training in careful
attention to detail, and by means of them girls have learnt much
concerning the food of plants. The experiments have also
aroused much interest in wider circles. An article written years
ago, which described, among other experiments, some of the
water-culture experiments, brought letters from all parts of
England and even from distant lands, asking for advice.

The water-culture experiments at J.A. G. S. were thought
to be of such practical importance that one year the organ-
izers of the Bath and West Agricultural Show asked that
some of the plants in normal and abnormal food solutions
might be brought to the Agricultural Show on Clifton Downs,
so that farmers might see tKem. In spite of great difficulties in
taking the plants by cab and by train they were exhibited at
Bristol to farmers and others, and were brought back to Dulwich
and survived the journeys.

IV
TRANSPIRATION. RESPIRATION

TRANSPIRATION

MEMBERS of the class have often noticed that when plants
have been under bell-jars, or ferns in a glass case, moisture
has collected on the inside of the glass. Has it come from the
soil, or the plant, or from both soil and plant?

Pots containing damp soil are put under dry bell-jars, and a
liquid collects on the inside of the bell-jar. In making experi-
ments, therefore, to see if the plant gives off water, it is necessary
to cover the soil with india-rubber sheeting, or some other
substance through which water cannot pass. But when this
has been done, and the pot without a plant is placed under a
dry bell-jar, moisture again collects on the inside of the jar. It
is, therefore, necessary to cover the pot as well as the soil with
india-rubber sheeting.

Experiments are then made on plants, such as geraniums or
fuchsias, each pair of girls having a plant. The soil and pot
are covered with india-rubber sheeting fitting close to the vase-
lined stem, the pot is placed on a piece of glass, and a dry bell-
jar put over plant and pot. The junction of the glass plate and
bell-jar is vasclinecl, and the experiment left in the light. A
control experiment, similar to the last with the exception of
having no plant under the bell-jar, is set up in order to see if any
liquid condenses from the air. The inside of the bell-jar over the
plant becomes misty and then drops of liquid are clearly seen.
What is this liquid? It must not be taken for granted that it
is water. Various tests are suggested and applied, and in
hundreds of experiments the following results have been noted:

1. The liquid is colourless.

2. Blue cobalt chloride paper turns pink in the liquid.

3. Anhydrous copper sulphate (white) becomes blue when
placed in the liquid.

The plant in the light has given off water in the form of
vapour. In the control experiment no drops of liquid have
been seen.

TRANSPIRATION. RESPIRATION 23

How does this water escape from the plant? Are there pores
in the leaves too small to be seen by the naked eye? Each year
the girls studying transpiration pick leaves in the garden, pre-
ferably those with a petiole, and pressing the petiole firmly
between the fingers, put the blades into very hot water. The
heat expands the air in the leaf-blades, and bubbles are
noticed coming in streams from the leaves. In some leaves, such
as black poplar, birch, cow-parsley, laurel, lilac, vine, wood
sorrel, yellow dead-nettle, the bubbles are seen on the lower
surface only; in others, as floating pondweed, meadow grass,
sheep's fescue grass, water crowfoot, on the upper surface only;
and in others, as bluebell, clover, daffodil, sunflower, on both
surfaces.

After the results of each girl's experiments have been noted,
reference is made to results recorded in previous years. In
eight years the leaves of 298 species have been tested.

Leaves with pores on lower surface only, 197, 66- 1 per cent.
,, ,, ,, upper surface only, 18, 6-0 ,,
,, both surfaces, 83, 27-85

298

After the leaves have been treated in the above manner, and the
presence of bubbles has indicated on which surface the pores
(stomates) are to be found, pieces of the skin (epidermis) are
taken from similar leaves with forceps or a razor, mounted in
water on slides, and examined under the microscope. 1

Drawings are made of the guard-cells and other epidermal
cells, and also the pores if open. The stomates of the majority
of leaves close when surface sections are placed in water, but
in some they remain open.

Transverse sections of typical leaves are then placed under
microscopes, and each member of the class draws one. It is
difficult, as there has been little previous experience in using a
microscope, but a knowledge of the minute structure of a leaf
seems essential when studying various processes such as trans-
piration or respiration. Also, it gives some acquaintance, even
if only a very slight one, with the wonders revealed by a micro-

1 Stomates in leaves of floating pondweed, lesser celandine, marsh marigold,
and water starwort can be examined without cutting sections, or stripping off the
epidermis.

24 EXPERIMENTS IN LABORATORY

scope. Generally the study of a simpler structure, such as a
filament of Spirogyra from the pond, precedes the study of a
transverse section of a leaf.

Stomafe

Guard cell containing
chloroplasts with search

W Brenchley

FIG. 9. Surface view of stomates in lower
epidermis of laurel leaf (magnified).

Cuticle

Chloroplasts

with starch

Xylem

Sheath of

vascular bundle

Intercellular

space

Guard cell---""
Stomatc''

--Upper epidermis

Mesophijll

Lower epidermis

W Brcnchtey
FIG. 10. Transverse section of leaf blade of laurel (magnified).

The majority of leaves have pores on their under surfaces. .
Is more water given off from that surface in most leaves?

i . Pieces of filter paper, that have been previously dipped
in a solution of cobalt chloride, are dried until they are of a
deep blue colour, and each leaf, after being carefully wiped,
is put with forceps on a piece of cobalt paper resting on a
dry glass slide. A second piece of dry cobalt paper is put
over the leaf, and then another glass slide. (The slides should
project beyond the edges of the paper.) The whole is held
together, or secured with india-rubber bands. As a control

TRANSPIRATION. RESPIRATION 25

experiment a dry piece of cobalt paper is put between two glass
slides.

The change of colour from the blue of the dry cobalt paper
to pink when water is present is easily seen, and shows when
water is being given off by the leaf.

Older girls, specializing in science, often examine the leaves
that have been tested in this way and find that the surface from
which water has been given off is the surface in which stomates
are present.

2. The cut ends of petioles of leaves, such as laurel, are
vaselined, and cotton-wool bound round them to prevent water
escaping through the petioles. Vaseline is rubbed over the
upper surface of some leaves, and over the lower surface of
others, and the leaves are suspended in a well-lighted place.
After a time the leaves which have only the upper surface
vaselined are wilted, while the leaves with only the lower surface
vaselined are still fresh. More water is given off from the lower
surface of laurel leaves than from the upper. It has already
been seen in previous experiments that in laurel leaves the
pores (stomates) are only on the lower surface, so again the
connexion between the presence of stomates and the giving off
of water has been shown.

Leaves from the india-rubber plant are even better than laurel
leaves for the above experiment. With the lower surface vase-
lined the leaves sometimes keep fresh for weeks when those
with only the upper surface vaselined are wilted.

From the above experiments it is seen that water is given off
in the form of vapour through the stomates the plant tran-
spires.

The rate of transpiration can also be measured. There are
different forms of apparatus called potometers. The one shown
in Fig. 1 1 is the one most used at Dulwich, although other forms
are also used. It consists of a gas-jar (or bottle with a wide neck)
fitted with an india-rubber cork with three holes. Into one
hole is inserted a piece of glass tubing of narrow bore, shaped
as in the diagram, into another a dropping funnel with a
stop-cock, and into the third a shoot. The shoot is cut from a
plant, under water, and it is better to do this some time before
it is wanted, keep it with the cut end under water, and cut off
under water a short length, before placing it in the potometer.

4158 F

26 EXPERIMENTS IN LABORATORY

The whole apparatus must be fitted up under water. 1 When the
tube, full of water, and the funnel and shoot have been placed
in the holes of the cork, the cork is pressed into the jar, the stop-

,

FIG. ii. A Potomctcr. (Farmer's form.)

cock closed, and the apparatus lifted out of the water. If the stem
of the shoot does not fit tightly into the hole, wax must be used.
The apparatus is placed in a good light and the stop-cock
turned until the water reaches the open end of the tube. As
water, in the form of vapour, is given off by the leaves, water
is taken from the jar, and the water in the tube recedes. The

1 See appendix. Advantage of a deep sink.

TRANSPIRATION. RESPIRATION 27

advantage of this form of potometer is that when a fresh reading
is required the stop-cock can be turned and water again reaches
the end of the tube. It is not an expensive piece of apparatus,
it is set up by each pair of girls, and many results are recorded.

The volume of water taken up by the shoot in a given time
is easily found;

Let L = length of tube along which r^^^^V
water has receded. f//\ ^

Let D = internal diameter of tubing,
radius (r) = \D.

Volume of water absorbed by shoot =

TT-

FIG. 12. Experiment to
compare rates of absorp-
tion and transpiration.

(In all potometer experiments the aver-
age of 2 or 3 readings should be taken
as the rate.)

For making quick comparative records
capillary tubing is used, a bubble of air
introduced, and the time noted for the
bubble to travel between two given
points.

It is the rate of absorption that is mea-
sured by this apparatus, and it is usually
assumed that the rate of absorption is
proportional to the rate of transpiration.
Experiments are made to see if this is usually the case.

To compare the rates of absorption and transpiration.

A ^JJ-tube is used with its long arm graduated in cubic centi-
metres (Fig. 1 2) . A shoot, which has been cut under water, is fitted
under water into the short arm. After the tube is taken out of
the water and dried, a little oil is poured on the surface of the
water in the open end to prevent evaporation. The apparatus
is suspended by wire from the arm of a chemical balance, the
weight in grams noted, also the volume of water in the tube.

The apparatus is left in a good light, and readings are taken
at intervals, showing the volume of water absorbed and the
difference in weight. In many experiments at J.A.G.S. the
amount absorbed was approximately the same as that trans-
pired (see later), and in using the potometer shown on p. 26 it
is taken that this is the case.

28 EXPERIMENTS IN LABORATORY

But the two amounts are not always the same, 1 and for that
reason some prefer to measure transpiration by changes in the
weight of a plant. This method also is open to criticism, as it
assumes that the change in weight is caused only by loss of
water, and does not take into consideration the gain in dry
weight due to photosynthesis, and the loss due to respiration.
But numerous experiments elsewhere have shown that the error
caused by neglecting photosynthesis and respiration is only a
fraction of i per cent. (See Maximo v, The Plant in Relation to
Water.)

In addition to the potometer experiments the following one
is made by all pupils at J.A.G.S., when studying transpira-
tion. A plant in a pot is well watered, the soil and pot covered
by rubber sheeting, and the pot then placed on a compression
balance in a good light. The weight is noted at intervals. The
rate of transpiration is determined by the loss of weight in a
given time.

Rate of transpiration under varying conditions. By using
a potometer under varying conditions the following results have
been obtained, an average of several readings in each case being
taken after allowing time for adjustment to the new conditions.

1 . Transpiration is greater in bright sunlight than in shade,
and greater in light than in absence of light.

2. Transpiration is greater in moving air than in still air.

3. Transpiration is greater in dry air than in moist air.

4. Transpiration is greater in warm air than in cold air.

RESPIRATION

Do plants take in oxygen and give out carbon dioxide?

To determine whether carbon dioxide is given out experiments
are made with (a) seeds and colourless seedlings, (b) green plants.

The apparatus is arranged as shown in Fig. 13. Fitted
Wolff's flasks are used, or jars with rubber corks. The various
connexions must be air-tight, the tubes through which air enters
the flasks A, B, C, and D should reach nearly to the bottom of
the flasks, and the ends of the tubes, through which the air
leaves the flasks, should be high in the flasks.

1 Eberdt showed in one set of experiments that in the day-time transpiration
exceeded absorption, and in the evening absorption was greater than transpiration.

TRANSPIRATION. RESPIRATION 29

When the tap of the aspirator is turned, a current of air is
drawn through the apparatus. Caustic soda in flask A absorbs
the carbon dioxide of the air, lime water in flask B shows if the
air is free from carbon dioxide. After the air, freed from carbon
dioxide, has passed through flask C, in which are a number of
colourless seedlings and soaked seeds on a wet pad, it passes
through flask D, containing lime water.

A control experiment is set up similar to the above, differing
only in having no seeds and seedlings. At the beginning of the

FIG. 13. Apparatus for seeing if carbon dioxide is given off by germinat-
ing seeds (or colourless seedlings).

experiment air is drawn through both pieces of apparatus, so
that no carbon dioxide shall be present, and then the taps of the
aspirators are shut. At the next lesson the taps of the aspirators
are turned. Scores of experiments have been made and results
recorded.

1 . The lime water in B in both sets remains clear.

2. The lime water in D in the experiment which contains
seeds and seedlings becomes cloudy ('milky 5 ).

3. The lime water in D in the experiment without seeds and
seedlings remains clear.

Seeds and colourless seedlings give out carbon dioxide.

(b) A green plant under a bell-jar fitted with a cork and two
tubes is used instead of seeds and colourless seedlings in a Wolff's
flask. The bell-jar stands on a piece of glass, and the junction of
the bell-jar and plate is smeared with vaseline, so that no air
can enter. The same method is used as in the last experiment,
but the lime water in flask D does not become milky. What is

30 EXPERIMENTS IN LABORATORY

the explanation? It has already been seen that green plants in
the light take in carbon dioxide, make sugar and starch, and
give out oxygen. It is, therefore, necessary, if we wish to see if
respiration takes place in green plants, that the plant should
not be in the light. A black paper cover is put over the bell-
jar, and after a time a current of air is drawn through the
apparatus. As in the previous experiment with seeds and
colourless seedlings ( i ) the lime water in flask B remains clear,
(2) the lime water in flask D becomes milky.

-Tube of causfic soda

M. Spring

FIG. 14. Apparatus for seeing if germinating seeds take in oxygen.

In a control experiment the apparatus is set up without a
green plant. The lime water in D does not become milky.

A green plant in the absence of light gives out carbon dioxide.
In the light the carbon dioxide is used in photosynthesis and
none leaves the plant.

It has been shown that plants give off carbon dioxide. Do
they take in oxygen?

It is not conclusive to see a lighted splinter go out when intro-
duced into a jar containing germinating seeds. This might be
caused by the reduction of oxygen, or by the presence of carbon
dioxide. Some substance, such as caustic soda or potash, which
absorbs carbon dioxide, can be introduced.

A useful piece of apparatus is shown in Fig. 14. The side tube
of a filter flask is connected by india-rubber tubing and wire
with a long piece of glass tubing the end of which is bent at
right angles. Some pea seeds, which have been soaked and
are beginning to germinate, are placed on a wet pad in the flask,
inside which a short test-tube containing caustic soda is sus-
pended by cotton, and a well-fitting india-rubber cork is put in
the flask and holds the cotton in position. The air in the flask
is warmed by holding the flask in the hands, and the end of

TRANSPIRATION. RESPIRATION 31

the glass tube is put in a basin containing mercury. As the air
in the flask cools the mercury travels up the tube. When it
is stationary the position is
marked. An experiment in-
which there are no seeds is
fitted up as a control. After
a time it is noticed that the
mercury has travelled along
the tube in the first experi-
ment, but is nearly in the same
place as it was, in the control
experiment. A lighted splinter
put in the first flask is extin-
guished, but is not extinguished
when put into the flask of the
control experiment. Oxygen
has been taken in by the seed-
lings during respiration.

Plants when respiring take
in oxygen and produce carbon
dioxide.

To find the value of the
respiratory coefficient in pea
seeds. (To compare the
volume of carbon dioxide
given off and the volume of
oxygen taken in during res-
piration.) The apparatus used
is shown in Fig. 15. Damp
cotton-wool is put at the bot-

FIG. 15. To compare the volume of

torn of the wide part of one of gases takcn in and given off during
the tubes and then a few pea respiration,

seeds in early stages of ger-
mination. The other similar piece of apparatus is used as a con-
trol experiment. Water is drawn by suction from the beakers
until it is at the same level in both graduated tubes, the taps are
turned, and clips fastened, so that air cannot enter. The level
of the water is read at intervals. Change in the level of the
water shows a change in the volume of the air above the water.

32 EXPERIMENTS IN LABORATORY

The control experiment is arranged in order to see if any
difference in the volume of the air is due to change of tempera-
ture of the air of the room. One set of records was as follows:

Date

Feb. 2

3

4
5

Height of water in

apparatus contain-

Height of water in

Time

ing pea seeds

control experiment

cm.

cm.

11.30 a.m.

30-0

30-0

4 p.m.

3'5

30-5

5 p.m.

31-0

31-0

1.30 p.m.

3!'5

31-0

9.45 a.m.

31-5

3 i-8

The results of many experiments at J.A.G.S. show that in
the early stages of germination of pea seeds the volume of gas
given off equals the volume of gas taken in.

_, . /carbon dioxideA

1 he respiratory coemcient

\ oxygen /

i.

Respiration in seeds containing oil. The same apparatus
is used as in the last experiment, but, instead of pea seeds, sun-
flower seeds which contain oil arc used. One set of records, as*
an example, is given below.

Date

Time

Height of water in
experiment with
sun/lower seeds

Height of water in
control experiment

cm.

cm.

May 25
26

10 a.m.
9 a.m.

43-5
45*0

42-0
38-0

10.20 a.m.
1 1 a.m.
12 noon

43*0
43'6
43'2

37-0
36-6
36-2

1.50 p.m.

42-5

35'3

27

4.45 p.m.
9 a.m.

41-5
40-7

34*i
37-6

The volume of gas absorbed by germinating sunflower seeds
during respiration is greater than the volume of gas given off.
The respiratory coefficient for sunflower seeds

/carbon dioxide\ . .
j 1S i e ss than i .

\ oxygen /

Is there a change of temperature during the process of
respiration? It is well to take actively respiring parts of plants

TRANSPIRATION. RESPIRATION 33

such as seeds or flowers. A number of pea seeds which have
been soaked in water and are in the early stages of germination
are put in a beaker. In a control experiment a beaker of the
same size is filled with pea seeds which have been killed by
being put in boiling water for a short time. In order that
mould or bacteria may not develop on the dead pea seeds a
trace, and only a trace, of corrosive sublimate is put in the
boiling water in which the seeds are placed. Corrosive sub-
limate is a deadly poison, and, if preferred, the pea seeds may
be placed in a boiling solution of permanganate of potash for a
short time. Several thermometers, reading to J or degrees,
are placed in a beaker containing water, and two which register
the same are used, one being put in the midst of the living pea
seeds and one in the dead seeds. In each case the bulb of the
thermometer is buried in the seeds. A bell-jar is put over each
of the beakers, and the stem of the thermometer comes out
through the neck of the jar. The space round the thermometers
in the neck is packed with cotton-wool.

Readings of temperatures registered by both thermometers
are taken at intervals.

RISE OF TEMPERATURE IN RESPIRATION

Date

Time

Temp, of living
seeds

Temp, of dead
seeds

Diff.

G.

C.

C.

March 20

9 a.m.

15-0

14-3

0-7

3 P- m -

1 8-6

17-0

6

21

9 a.m.

17-1

16-0

i

,,

4.15 p.m.

18-7

17-4

'3

22

9 a.m.

16-5

157

0-8

3 p.m.

17-8

16-2

6

}>

3.8 p.m.

i7'9

16-2

7

4.30 p.m.

17-2

16-3

0-9

The temperature of the germinating pea seeds is higher than
the temperature of the dead seeds.

(More striking results are seen if thermos flasks are used.)

Can plants respire without oxygen? Two test-tubes are
filled with mercury and inverted in bowls of mercury. (It is
well to fit up this experiment on a tray.) The testas of some pea
seeds which have been soaked are removed, so that air from

4158 T?

34 EXPERIMENTS IN LABORATORY

between testa and seed is not introduced, and the seeds are
slipped into one of the test-tubes. They rise to the top of the
mercury. Black caps are put over the tubes. After a time the
mercury is much lower in the test-tube containing the pea
seeds. It seems as if some gas has been given out by the germi-
nating pea seeds. A piece of caustic soda, or potash, is put into
this tube and rises to the top. The mercury again fills the test-
tube, the gas has been absorbed. In the control experiment,
the one in which there are no pea seeds, the mercury has not
sunk in the tube.

Carbon dioxide has been given out by the germinating pea
seeds, although no oxygen has been absorbed. This process is
called anaerobic, or intra-molecular, respiration, and can only
go on for a time.

Summary. During respiration oxygen is taken in and carbon
dioxide produced, but this is not the whole of the process. The
rise of temperature during respiration shows that energy has
been liberated. Substances, such as carbohydrates, undergo
combustion in the presence of oxygen, carbon dioxide is formed,
and energy released. As a rule the volumes of gas taken in and
given out are equal. Anaerobic, or intra-molecular, respiration
can go on for a time in the absence of oxygen.

V
GROWTH IN PLANTS. DIRECTION OF GROWTH

I

IS growth in length in plants restricted to definite regions in
roots and stems?

The root. Well-developed, straight radicles, about an inch
long, of runner beans, which have been growing in damp saw-
dust, are dried with blotting-paper, and on them horizontal
lines, one millimetre apart, are marked in Indian ink, beginning
at the tip. The seedlings are pinned through the cotyledons on to
a piece of sheet cork with the roots pointing vertically down-
wards, the piece of cork is wedged into ajar containing a little
water, and a stopper or cork put in the jar. The jars are put
in the dark until the next lesson.

It is then seen that there are no longer equal distances
between the marks. The maximum growth in length of the
root has taken place a little above the tip. At the tip itself
there is little or no difference in the interval between two suc-
cessive marks, but for a short distance the intervals become
wider until the maximum is reached; after that there is a
gradual decline in the length of the interval until near the
cotyledons the interval only measures the original millimetre.
(See Fig. 1 6.)

The stem. Horizontal lines in Indian ink are marked on the
plumules of runner beans, and pea seedlings, and the hypocotyls
of sunflower, in every case beginning at the tip.

Again, after a short time, the lengths of the intervals are found
to be unequal. The region of maximum growth is some dis-
tance below the tip, and the lengths of the intervals gradually
decrease on each side. (See Fig. 17.)

On comparing the regions of elongation in the root and
stem of a runner bean it is seen that it extends farther
in the stem than in the root. In the stems of some plants
regions which are several centimetres from the tip grow in
length.

FIG. 1 6. Graph showing region of growth in radicle of Pea. Average
result of 9 experiments. Lengths of verticals represent distances after 3 days
between marks originally i mm. apart.

GROWTH IN PLANTS. DIRECTION OF GROWTH 37

9 10

J Pocock

FIG. 17. Graph showing region of growth in hypocotyl of Sunflower.
Average result of 10 experiments. Lengths of verticals represent distances
after 3 days between marks originally i mm. apart.

The results of nine experiments made by members of a class,
showing which parts of sunflower hypocotyls grow most quickly,
are seen in the following table.

CLASS RESULTS. THE GROWING REGION IN THE HYPOCOTYL OF

SUNFLOWER

Spaces between

marks

1-2

2~3

3-4

4-5

5-6

6-7

7-5

#-.9

g-io

mm.

mm.

mm.

mm.

mm.

mm.

mm.

mm.

mm.

*5

!'5

2

2

2

2

2'5

i'5

'5

i'5

2

2

2

i'5

i'5

I

2

2

3

2

2

2

2

2

3

2

2

3

2

2

5

2

2

2

2

2

'5

i'5

'5

2

2

2

2

i'5

I

i

2

2

i'5

i-5

2

1-5

i'5

'5

'5

2

2

i'5

*'5

2

i'5

i'5

i'5

2

2

3

3

3

2*5

2

2

'5

Average

i'5

i'9

2'I

2'I

2'I

i'9

1-7

i'5

i'i

Note. Lines originally i millimetre apart.

Accurate measurement of growth in length. 1 An instru-
ment known as an auxanometer (Fig. 18) is used to make
accurate measurements of the growth in length of an organ
during a stated period. There are many forms. At Dulwich
the same instrument has been in use for nearly thirty years, and
a great number of experiments have been made with it. Care

1 See also Darwin and Acton, Physiology of 'Plants , 1909.

38 EXPERIMENTS IN LABORATORY

is required in setting it up. The tip of the stem of a plant in a
pot is fastened by thread to a hook at one end of the lever.
Attached to the other end of the lever is a triangular piece of
stiff glazed paper, bent so that its pointed tip can 'write' on the
blackened paper (see appendix) which surrounds the drum.

FIG. 1 8. An auxanometer (Farmer's).

Fulcrum (F) opposite middle of drum (X). A'F = 7 FG. S, sliding clip (wilh
hook for light weight if needed), to bring tip of lever at start of experiment to posi-
tion A (without undue tension of thread).

The lever is balanced on a knife-edge, and it should be arranged
that the arm which is nearer the drum is several times the length
of the arm which is nearer the plant. Projecting from the base
of the drum is a piece of metal which is struck every hour, or
half-hour, or quarter-hour by the minute hand of the clock,
and thus the drum, which can revolve a short way, is carried
a little way with it. An arrangement is present above the drum
which brings it back to its original position after it has revolved.
As the stem grows in length, the end of the lever connected

GROWTH IN PLANTS. DIRECTION OF GROWTH 39

with the stem is raised, and the other end lowered, and the
tongue, which rests against the blackened surface of the drum,
makes a longitudinal mark. At regular intervals (one hour is
a convenient period) the 'hand' of the clock hits the projection
on the drum and causes it to revolve; when the drum swings
back a short horizontal mark is made. The vertical distance
between two successive horizontal lines gives the apparent
growth in length of the stem in one hour, but is really as many
times the actual growth in length as one arm of the lever is
longer than the other.

By means of the auxanometer it can be shown that the rate of
growth in length is greater in the absence of light than in its
presence, provided that the temperature is approximately the
same. The influence of temperature on the rate of growth can
also be demonstrated.

DIRECTION OF GROWTH

i. Influence of water .

The root. Occasionally when the flap in the poncl (see p. 82)
has been lifted the water has not run away, and a wet place in
the grass, sometimes at a distance, has shown that water cannot
pass in the pipe underneath. On investigation it has been found
that the drain pipes no longer fit against each other, and are
crowded with roots. The water seems to attract the roots.

In the laboratory experiments have been made to see if
growth curvatures in roots can be produced by the presence of
water. Damp sawdust is put in two sieves to the depth of about
half an inch and cress seeds are scattered, on the surface. The
sieves are placed in the dark, at an angle of 45, in basins con-
taining some water. When the seeds germinate, and the roots
are growing downwards towards the bottom of the basins, the
water is emptied from one basin and left in the other. The
sawdust in both sieves is kept moist. The roots of the seedlings
over water continue to grow downwards, but the roots of the
seedlings which have no water below them grow towards
the damp sawdust. On one side of these roots the damp sawdust
is much nearer than on the other, owing to the inclination of the
sieve, and the roots grow towards this part.

The presence of water has an influence on the direction of
growth of roots.

40 EXPERIMENTS IN LABORATORY

2. Influence of light.

(a) The stem. It is known to most people that if plants are
placed near a window, or other place illuminated on one side
only, their stems grow towards the light.

1. In the laboratory a hole has been cut in the door of a
cupboard, and a plant, such as a geranium or fuchsia, with a
well-developed straight main stem, is put in the cupboard. The
stem grows out through the hole towards the light and the leaves
have their flat surfaces at right angles to the direction of the rays
of light (Fig. 19). If the plant were put on the floor of the cup-
board, or on blocks on the floor, each time the door was opened
the stem and leaves would be dragged back through the hole, so
a small shelf has been attached to the door itself, and the position
of the stem and leaves is unaltered when the door is opened.

2. Other experiments showing the influence of light on the
direction of growth of stems are made on mustard seedlings
(Fig. 20). Coarse muslin is tied loosely over the top of a number
of gas-jars, so that it sags a little. Water is poured in the jars
until it just touches the muslin, mustard seeds are put on the
muslin, and the jars placed in the windows. The seeds soon
germinate, and first the hypocotyls and then the plumules grow
towards the source of light. If the jars are turned through 180
the young parts of the stems again grow towards the light, and
if this is repeated the stems have a sinuous appearance. In the
control experiments black paper is tied all the way round the
jars and projects well above the top of them. The stems grow
straight up, and the roots downwards.

(b) The root. If from the beginning of the experiment black
paper is tied round the jars, except for a narrow longitudina 1
chink, and the jars are placed in the windows with the chink
facing the light, it can be seen that the roots of the mustard
plants grow away from the light.

If when the jars are turned through 180 the position of the
black paper is altered, so that the chink again faces the light,
the roots of the mustard again grow away from the light.

But other experiments have shown that in many plants
light does not have a directive influence on the growth of
roots.

FIG. 19. Stem of Geranium plant growing through
hole in cupboard door towards the light.

Direction of light

L- KIMBER

FIG. 20. Influence of light on direction of growth of hypocotyls of mustard
B. Jar turned through 180 from its first position (A).

4158

42 EXPERIMENTS IN LABORATORY

Region of light perception. Is there in some plants a part
which is particularly sensitive to the stimulus of light? Some
Italian Millet (Setaria) seeds are sown in a pot, and while the
leaves of the seedlings are still within the plumular sheath, the
tips of some are covered by caps made by twisting tinfoil round
the point of a pin. The pot is put in a box with light coming
through a narrow slit from one direction only.

At the next lesson it is seen that the uncovered coleoptiles
have bent towards the light, but not those covered at the tip.
The upper part of the coleoptile of Italian Millet is therefore
the perceptive part, or at least much more sensitive than the
lower. The part which actually curves is at a little distance
below the tip.

Recent experiments. Influence of light on direction of
growth. Experiments have been made by a number of observers
on the tips of coleoptiles of various members of the family
Gramineae. In 1919 Paal described experiments in which the
tips of the coleoptiles of a grass (Coix lacrima), after exposure to
one-sided illumination, were cut off and put eccentrically on the
stumps of other coleoptiles, which had not been exposed to
one-sided illumination, with the result that the coleoptiles
curved away from the side covered by the tip. It was concluded
that a substance formed in the tip had diffused into the stump
and accelerated cell growth in the elongating zone.

F. W. Went first definitely proved (1926) that a growth-
accelerating substance was produced in the tips of coleoptiles.
He cut off the tips of some coleoptiles of oat seedlings and placed
them for an hour on a thin block of agar, a substance something
like gelatine. The block was then cut into small pieces of equal
size and each piece stuck on one side of the cut surface of a
coleoptile which had just been decapitated. The coleoptiles so
treated curved away from the side covered by the agar. 1

The name 'auxin' has been given to this growth-accelerating
substance, and it has been shown that when there is one-sided
illumination of the coleoptile there is less auxin on the side
towards the light than on the other. Curvature towards the
illuminated side is the result.

1 R. Snow, 'Growth Regulators in Plants', New Phytologist, 1932.

GROWTH IN PLANTS. DIRECTION OF GROWTH 43

3. Influence of gravity.

(a) The root. The main root of a plant is generally observed
to be growing vertically downwards. Experiments are made to
try to find the cause of this downward growth.

1. Is it the weight of the root? Corks, cleft at the base, are
wedged on to the edge of a basin containing mercury, and young
bean and pea seedlings, with straight radicles, are pinned on
the corks so that the radicles are horizontal, and supported by
the mercury. Strips of blotting-paper, with one end in a basin
of water, are laid along the seedlings to supply the roots with
water. It is well to have the experiment on a tray in case
mercury should be spilt. The experiments are put in the dark,
and bell-jars placed over them. After a short time it is seen that
the roots have grown down into the mercury. The weight of
the mercury displaced is greater than the weight of the root, so
the downward growth of the root is not due to its weight.

2. Other experiments are then made. Young runner bean
seedlings with straight radicles, about one to one and a half
inches long, are pinned on a sheet of cork. Some of the roots
point vertically upwards, some are horizontal, and some are in
other positions. The piece of cork is fitted into a wide-mouthed
stoppered jar, and the jar put in the dark so that light shall have
no influence on the direction of growth, but moisture must be
supplied or the roots will die. If water is put in the jar, and the
roots grow downwards, it might be concluded that the presence
of water at the bottom of the jar has caused the downward
growth of the roots, so a piece of wet cotton-wool is stretched
across the top of the jar and kept in position by the lid. The
air in the jar is thus kept moist.

In a day or so all the roots are growing vertically downwards.
The direction of growth has not been influenced by light, nor
by the presence of water. It seems as if gravity has an influence
on the direction of growth of roots.

3. A piece of apparatus called a clinostat is used. It is so
constructed that a plant can be rotated slowly in a vertical or
horizontal plane. If a plant, or seedling, with its root and stem
horizontal, is rotated in a vertical plane, all sides of the root
and stem in succession are subjected to the influence of gravity,
so the influence of gravity is equally distributed. A form of

44 EXPERIMENTS IN LABORATORY

clinostat used for many years at Dulwich is shown in Fig. 21.
In experiment after experiment it is seen that when the plant
or seedling is rotated slowly (four times in the hour) in a vertical
plane in the dark, there is no curvature of the root, although
in a control experiment near the clinostat, in which the root is
horizontal, downward curvature does take place. 1

flQ

FIG. 21. A clinostat.

The works of a powerful eight-day clock, geared to a revolution in 1 5 minutes,
are encased in a drum (A) . A spindle rod (B) is attached to the drum and rests on
a vertical support. At the end of the rod is a disk (C) with screw rods by means of
which a plant can be attached to the disk. The weight of the plant must be centred.

Perception of gravity in a root. Experiments similar to those
made by Charles Darwin 2 are made by every member of the
class. The extreme tips of the roots of some young pea seedlings
arc cut off and the seedlings pinned, as in Experiment (2), on
a sheet of cork with their roots pointing in various directions,
but not vertically downwards. Other seedlings, with their tips
intact and pointing in similar directions, are placed on the same
sheet of cork, and the cork wedged into a jar, which then has a
stopper put in it, and is placed in the dark. The roots without
tips usually grow, but do not grow downwards until new tips
have been developed. The roots with tips, as in Experiment (2),
grow vertically downwards. The region of perception of gravity
in a root seems to be the tip.

1 The clinostat can also be used to secure equal illumination on all sides when
a plant is rotated in a horizontal plane.

2 Giesielski was the originator.

GROWTH IN PLANTS. DIRECTION OF GROWTH 45

If, however, the seedlings are put with the roots horizontal
for a short time, and then the tips are cut off, the roots do grow
downwards.

Experiments have also shown that if horizontal lines are
marked in Indian ink on the roots and stems of seedlings, at

FIG. 22. Influence of gravity on the direction of growth of sterns. Bean
seedling after it had been placed in the dark with its stem horizontal.

equal intervals, and the roots and stems placed horizontally,
the region of maximum elongation is the region of curvature.

Recent work on the perception of gravity in roots has shown
that if the tip from a root of maize, which has been in a hori-
zontal position, is stuck on the stump of a decapitated root,
which has been vertical, curvature follows. The curvature is
stated to be caused by a redistribution of a growth-regulating
substance in the tip. 1 Other experiments have been made show-
ing that the growth-regulating substance, which is growth-

1 Keeble, Nelson, and Snow, Proc. Roy. Soc., 1929.

4 6

EXPERIMENTS IN LABORATORY

retarding, accumulates to a greater extent in the lower half of
the tip of a root placed horizontally than in the upper, and
curvature follows. 1

(b) The stem, i . Bean seedlings are placed in the dark with
the stems horizontal. Fig. 22 shows a drawing of the stem of a

Afrer 24 hours

Affer a week

FIG. 23. Influence of gravity on the direction

of growth of hypocotyls. Sunflower seedling

24 hours, and 7 days, after it had been placed in

the dark with its hypocotyl horizontal.

bean seedling growing vertically upwards after the seedling has
been placed with the stem horizontal, and Fig. 23 shows two
drawings of the hypocotyl of a sunflower, 24 hours and also
7 days after it was horizontal.

2. Geranium and fuchsia plants are turned upside down on
a tripod, the top of the pot first being covered to prevent earth
1 Hawker, New Plwtologist Dec. 1932.

GROWTH IN PLANTS. DIRECTION OF GROWTH 47
falling out. For some years pieces of cardboard were used, but
these became sodden when the plant was watered and plates of
tin were cut with a slit on one side, and a hole in the middle for
the stem. These cost very little and are used time after time.

It can be seen quite clearly from the diagram that the young
parts of the stems have grown away from the centre of the earth

S Kmgwill

FIG. 24. Influence of gravity on the direction of growth
of stems. Geranium plant turned upside down.

and that the upper surfaces of the leaves are again facing
upwards. Sometimes the inverted plants are placed in the dark,
sometimes in the garden in a place where, as far as possible, they
are equally illuminated on all sides.

3. The Clinostat. Plants have been placed in the clinostat with
the stem horizontal, and rotated for days in a vertical plane in
the dark. No upward curvature of the stem has taken place,
although, in a control experiment near the clinostat, the stem of
a plant which had been horizontal has grown upwards.

VI
THE SOIL

THE experiments described in this chapter are some of the
soil experiments made in the J.A.G.S. laboratory, many of
them each year for more than twenty years. Some of the soil
experiments in the garden were made much earlier. (See
Chapter XIII.)

1. To find the percentage of water lost when soil is air-
dried. Samples of soil are taken from various botany gardens,
such as the wood, the pollination beds, and the sand dune, and
each pair of girls weighs out a small quantity, say 100 gm.,
spreads it out, and leaves it exposed to the air in the laboratory.
At the next lesson the soil is re-weighed, and the process repeated
until the weight is constant.

2. To find the percentage of water still present in air-
dried soil. Some of the soil that had been air-dried in the pre-
vious experiment is put in a weighed evaporating dish, the
weight found, and the dish placed in a water-oven (temperature
approximately 100 C.). After a time the dish and soil are
weighed again, then replaced in the oven, and the process
repeated until the weight is constant.

The percentage of water still present in the air-dried soils
varies in the clay soils from the pollination beds, the soil from
the wood, and the soil from the sand dune.

(The various oven-dried soils may be kept in stoppered jars
and used in other experiments.)

3. To make a mechanical analysis of a soil. 1 Soil is brought
from the botany gardens and is air-dried. Some is shaken on a
sieve the meshes of which measure i millimetre. Stones, gravel,
and part of the organic remains (humus) are left on the sieve.

Five grams of the soil which passes through is put in a beaker
(A), and water is added to a height of three inches. The level
of the water is marked, the soil and water are stirred up and then

1 See Farmer, The Book of Nature Study, vol. v. The Caxton Publishing Company.

THE SOIL 49

allowed to settle for a minute. The water, which contains fine
particles of soil, is then poured into another beaker (B). This
process is repeated until the water in A is practically clear at
the end of a minute. The turbid water in B, which has been
poured from beaker A, is allowed to stand for a few days, then
the water is poured off, and the sediment oven-dried. This
sediment is silt and clay.

The sediment at the bottom of beaker A is also oven-dried,
and is then shaken in a sieve the meshes of which measure
| millimetre. Fine sand comes through and coarse sand is left.

The soil is thus shown to consist of humus, stones, gravel,
coarse sand, fine sand, silt, and clay.

RESULT OF ONE EXPERIMENT IN A TABULAR FORM

Weight

Percentage

Soil

Part which

Humus,

did not

stones,

pass through

gravel.

i mm. sieve.

Part which

did not

0-47 gm.

9'4

Coarse

pass

sand.

through

'Part which

fine sieve.

settled in

;

i minute.

Part which

Part which

did pass

did pass

3-6 gm.

72-0

Fine

through

through

sand.

i mm. sieve.

fine sieve.

Part which

did not

0-93 gm.

18-6

Silt and

settle in

(by cal-

clay.

^i minute.

culation)

In a mechanical analysis made of another soil the results
were as follows:

5 gm. taken after soil had been air-dried and stones
and gravel together with some humus removed

Coarse sand . . . 26-4 per cent.
Fine sand . . . 53-2

Silt and clay . . 20-4

4158 H

50 EXPERIMENTS IN LABORATORY

To compare the power of sand and clay to lift water.

Pieces of wide combustion tubing, 1 8 to 20 inches long, are used,
and fine muslin is tied over one end of each. One tube is filled
with oven-dried sand, and the other with oven-dried powdered
clay. (It is well to keep tapping the tubes when they are

Sand

FIG. 25. Apparatus for comparing the rise of
water in sand and clay.

being filled.) The tubes are held in clamp stands, and at the
same time are lowered, so that the ends covered with muslin
are in water in basins (see Fig. 25). The levels to which the
water rises in the clay and in the sand are noted at intervals.
The results on page 52 were recorded in one experiment. (Water
passes slowly into completely dry soils.)

In all the experiments that have been made the water has
risen more quickly at first in the sand than in the clay, but after
a time the level in the clay is higher and the water continues
to rise after the level in the sand is stationary.

THE SOIL 51

For demonstration purposes, in addition to the experiments
made by every pair of girls, two pieces of combustion tubing.

W. Datton

5 10 15 20 Z5 30 Days

FIG. 26. Graph representing rise of water in sand and clay.

several feet long, one filled with oven-dried powdered clay and
the other with oven-dried sand, as in the above experiment, are
kept in the laboratory.

A graph showing the rise of water in sand and clay is seen
in Fig. 26.

EXPERIMENTS IN LABORATORY

READINGS

Date

Height of water in cm.
in sand

Height of water in cm.
in clay

Oct. 30

21-0

o

3 1
Nov. i

2

27-0
28-0
29*2

9'5
13-5
18-5

3

29-2

23-2

4
6
8

30-2
30*2
30-2

25-2
26-7
29-2

13
15

3i*4
3''4

34'2
36-2

20

33'4

40-2

22

33'4

41-7

27

33'4

44-7

Finally

35-6 stationary

47-0 at top

To compare the permeability to air of sand and clay. Two

aspirators are filled with water, and each is fitted with an india-
rubber cork with one hole. Through the hole is put the stem
of a funnel which has been loosely plugged with a little cotton-
wool. Equal weights of oven-dried sand and clay are mixed
with equal quantities of water; some of the wet clay is put into
one of the funnels and the same amount of wet sand into the
other. The taps of the aspirators are turned; water runs out of
the aspirator with sand in the funnel, but little or none out of
the aspirator with clay in the funnel.

Sand is more permeable to air than clay.

To determine the water capacity of soil. A measured
quantity of water is put into a tin, and the level marked inside
the tin. The water is emptied out, and holes are knocked in the
bottom of the tin. Soil is put in the tin and shaken down until
it is at the same level as the water had been. The tin and soil
are then stood in a shallow dish of water until the soil is satur-
ated. Then the tin is taken out, and after the surplus water
has been allowed to drain away, the tin and soil are weighed.
The soil in the tin is then oven-dried until the weight is constant. 1

The difference in the weights of the tin and soil, when satur-
ated and when oven-dried, gives the weight of the water that

1 See Fritch and Salisbury, The Study of Plants. Bell & Sons.

THE SOIL 53

can be held by the measured volume of the given soil. The water
capacity can then be determined in terms of the volume of the
saturated soil since i c.c. of water weighs i gm.

In an experiment with peat from the bog in the J.A.G.S.
heath it was found that it absorbed 72-5 per cent, of the volume
of the saturated peat.

To determine the percentage of humus in soil. Soil is
taken from some part of the botany gardens and oven-dried.
A crucible is weighed, filled with the soil, and weighed again.
It is then heated over a Bunscn burner, or better still, in a
muffle furnace. The crucible is weighed at intervals and re-
heated until the weight is constant. It now contains a red
substance unlike the original soil. The percentage loss in weight
is found and it is assumed that the loss in weight is caused by
the disappearance of the decaying organic matter, the humus,
but it includes also any water that was previously in chemical
combination in the soil, and there may be slight loss of weight
of the ash constituents.

PERCENTAGE OF HUMUS IN VARIOUS SOILS
SUMMARY OF EXPERIMENTS MADE AT J.A.G.S. IN THIRTEEN

YEARS

No. of Percentage

Soil experiments (average)
Garden Soil

J.A.G.S. (Order Bed) 40 13-33

Heath Soil

J.A.G.S. 56 18-61

Keston 4 24-91

Bog Soil

J.A.G.S. 55 68-79

Keston 20 65-39

Wood Soil

Wood near Canterbury 10 24*32

New Wood, J.A.G.S.l

Dell } l8 2 4' 8 '

New Wood, J.A.G.S.l
Not Dell i 27 I2 '74

Influence of colour on temperature of soil. Two adjacent
similar plots of ground were hoed; one had a light dressing of

54 EXPERIMENTS IN LABORATORY

soot until the surface was black, and the other a dressing of
lime. A soil thermometer was put in each of the plots, the bulb
at a depth of G inches.

READINGS OF THERMOMETERS TAKEN DURING FOUR YEARS

No. of days on which
observations taken

No. of days on which
temperature of dark
soil higher

Percentage

No. of days on which
temperature of dark
soil the same

67

47

70-1

14

It was seen in the above experiments that on many days the
'black' soil absorbed more heat than the 'white'. The difference
was greatest on hot sunny days.

The temperatures of the light and dark soils on successive
school-days one June are shown below.

Date

Temperature of
light-coloured soil

Temperature of
dark-coloured soil

G.

G.

June 1 1

12

I5'9
16-0

16-1
16-2

15
16

17
18

16-9
17-6
i68
1 8-0

18-2
18-0
17-1
18-5

19

17-0

I7-3

Experiments showing the influence of aspect on the tempera-
ture of soils are described in Chapter IX. Other soil experi-
ments arc omitted for want of space.

THE BOTANY GARDENS

VII
HISTORY AND ORGANIZATION

'God Almighty first planted a garden. And indeed it is the purest of human
pleasures. It is the greatest refreshment to the spirits of man, without which
buildings and palaces are but gross handiworks.' BACON.

THE Botany Gardens of the James Allen's Girls' School,
Dulwich, were begun in 1896 and, as far as is known, were
the first gardens in a secondary school in England to be placed
in charge of the pupils and used for the purpose of teaching
botany. At that time many natural orders (now usually called
families) were included in the botany syllabus of some examina-
tions corresponding to the School Certificate Examinations of
the present day. In order that there should be a first-hand
knowledge of the plants belonging to these 'orders' between
twenty and thirty 'order' beds were made. The 'order' beds
soon formed only a part of the botany gardens. Plots for soil
experiments (development of root tubercles in leguminous
plants), plots for experimental work in carbon assimilation (as
photosynthesis was then called), and plots for pollination experi-
ments were added, also arrangements for climbing plants. A
small cornfield was made, a small sand dune, a salt marsh, a
chalk bed, a wood, and a bed for alpine plants, some addition
being made in most years.

For fifteen years there was no grant of money for the botany
gardens and the mistress and girls obtained some of the com-
moner plants. For some time there had been a great desire to
have a lane in the school grounds, and in 1909 the Governors
granted 10 for this purpose. The lane was made, and has
been of great service as well as a great pleasure. (See Chap. IX.)

Other developments were needed, the cost of which could not
be met by the girls, and application was made to the Board of
Education for a yearly grant. In 1912 the Board arranged to
make a yearly grant for at least three years. At the end of three
years it was renewed, and has been given every year since, thus
making it possible to have still further developments. These

56 THE BOTANY GARDENS

developments have included a large pond, a smaller pond,
freshwater marshes, salt marshes, more pollination beds, a
larger heath containing a peat bog, a larger wood, a larger
sand dune and pebble beach, a plot representing a meadow, a
cornfield, plots for Mendelian experiments and manurial experi-
ments, all added by degrees.

In 1926, the first year a census was taken, there were 591
species present in the botany gardens.

As already stated the work in the gardens is, and always
has been, voluntary. It is done in out-of-school hours. The
school is a day-school, and the chief time during which girls
work in their gardens is the dinner-hour recess. For the last
twenty years the average yearly number of girls in charge of
botany gardens has been nearly 300. In many years every girl
learning botany has had charge of a garden.

In the early days teacher and girls sometimes came in the
holidays to help make new gardens. If it had not been for the
enthusiasm shown by the girls, and the voluntary work done
by them, the botany gardens could not have been made. At
the present time girls, if they wish to work in the holidays,
are allowed to do so at stated times, and many do come.

In term time the girls work in pairs and choose their partners
from the same class. They have charge of a garden for a year,
and are entirely responsible for it. Having put their hands to
the plough they must not look back. Within certain limits
the girls choose which gardens they will have, but the girls of
the class, for example, studying water plants, must have charge
of the ponds and marshes, but they settle among themselves how
the parts shall be allotted.

The work is so arranged that a girl in the School Certificate
form, who has moved up steadily through the school from the
time she was about eleven, has had charge of parts of the lane,
wood, pond or marshes, heath and bog, and also a pollination
plot and an 'order' bed, in various years.

The botany gardens, in addition to being of immense help
in botanical and zoological work, are a great source of pleasure
in themselves to teachers and pupils.

The aesthetic aspect of the gardens has always been studied,
not only for the sake of the girls in charge of the various parts,
but for the sake of the school as a whole. In spring the lane

FIG. 27.

HISTORY AND ORGANIZATION 57

and wood with leaves of shrubs and trees unfolding, and prim-
roses, bluebells, campions, and violets in flower; in summer the
pollination beds and 'order 5 beds often masses of colour, the
ponds and marshes with water-lilies, purple loose-strife, and
meadow-sweet; in autumn the heath with heather and heath in
flower, all help to make the gardens beautiful. If some plants
belonging to a family are particularly beautiful, the girls in
charge can grow as many specimens
as space and the claims of other
plants permit.

Tools and tool sheds. Before 1912
the tools were generally supplied by
individuals, but one of the conditions
of the Board of Education grant was
that the girls were not to bear any
part of the expense of the botany
gardens.

As regards use and care of tools, the most satisfactory arrange-
ment is for each girl, or pair of girls, to use during the year the
same tools, and be responsible for them. For a long time there
were not sufficient tools to make this possible, but gradually as,
year by year, more were bought, they were numbered, and in
some forms each pair of girls had the sole use of a tool, and was
made responsible for its being in the right place in the tool shed.
Some wire hooks, suitable for holding small tools, such as hand-
forks and trowels, were found, price two shillings a dozen.
These hooks were screwed on the walls of the tool shed and
numbered, so that each small tool had its place. Also simple
brackets made of two pieces of iron, three-quarters of an inch
broad, bent at an angle, were fixed on shelves or other pro-
jections in the walls of the tool sheds, each to support a row of
larger tools, such as spades and forks (Fig. 27). A long bar was
also put down the middle of the sheds on which big spades
and forks could be hung.

It is important when there is not much time for gardening
that the workers should be able to find their tools easily, and
put them away tidily, especially if there are many working at
the same time. In the wood there are often sixty young girls
at work.

4158 T

58 THE BOTANY GARDENS

For many years there was no tool shed, and then for some
years only one small one, and no classification of tools was
possible, but after a time three tool sheds were put in different
parts of the garden. Rambler roses and other climbers were
trained over the sheds to make them harmonize with their
surroundings.

Labels. For sixteen years the girls paid for most of the labels,
each girl contributing two pence every year. Each plant, or
group of plants, had a small label with the English name on it.
Also excellent large oblong labels were made of tin, sometimes
8 inches long, nailed on wooden supports with a pointed end
to go into the ground. The wooden part was painted black, and
the tin part enamelled black, and the owners of gardens painted
names such as SALT MARSH in large white letters on the tin. It
is easy each year to re-enamel the labels, and repaint the names
if they have become indistinct.

Reports. At first only yearly reports were made of the
gardens, or parts of gardens, but for more than thirty years
monthly reports have been made on the work of the girls of each
class, and good individual work has been singled out for com-
mendation. There is also a report on the work of the year.
All the reports are usually read out in the Hall by the Head
Mistress.

Animal life. Although the object of this book is to give an
account of experiments on plants, passing references will be
made to the facilities the various gardens offer for the study of
animals. The gardens at J.A.G.S. may well be called biology
gardens.

Visitors. A great feature of the gardens has been the interest
they have aroused in people not connected with the school.
Teachers, and others interested in education, from Russia,
France, Germany, Spain, Portugal, Sweden, India, Ceylon,
South Africa, Australia, New Zealand, Japan, and the United
States, have visited them, and in France, Sweden, and Spain,
the J.A.G.S. botany gardens have been made the subject of
theses, when teachers and people in administrative posts have

HISTORY AND ORGANIZATION 59

returned home. Many teachers in our own country also have
visited the J.A.G.S. gardens. In the decade 1921-31 there are
on record the visits of nearly 800 people.

Formation of botany gardens elsewhere. There have been
numerous applications for information and guidance from those
wishing to make botany gardens, and it is in the hope that others
may benefit from the experience gained at Dulwich that practical
details of the various gardens are given in the following chapters.
The formation of botany gardens in schools in other parts of
the country by some who have been educated at J.A.G.S.,
and by others who have visited the gardens, has been a source
of great interest.

To any one who wishes to have botany gardens we would
say that the, great thing is to make a start, and not wait for
perfect conditions.

'To watch the corn grow, or the blossoms set; to draw hard breath over
plough-share or spade; to read, to think, to love, to pray these are the
things that make men happy.' RUSKIN.

VIII
POLLINATION EXPERIMENTS. CLIMBING PLANTS

VERY early in the history of the botany gardens plots for
pollination experiments were dug. In 1900 experiments
were made on garden pansies. After all the flowers had been
removed, one bed of pansies was covered with coarse muslin
on a frame, and close to it another bed was left uncovered.
Many fruits were formed on the uncovered plants, none on the
covered. Garden pansies do not form fruit when insects are
excluded. (Beds containing wild pansy plants were covered with
a muslin frame, and many fruits were formed.)

Experiments also were made to see if pollen is necessary for
the formation of fruit in various plants. Stamens, while still in
an unripe condition, were cut out of buds, and each bud was
enclosed in a fine muslin bag. Other experiments were made
to see if the shock of cutting out the stamens prevented the
formation of fruit. Unripe stamens were cut out of buds as
before, and then pollen from other flowers of the same species
was applied to the stigmas, and the flowers were marked by
tying cotton round the stalks. Very often the girls themselves
suggested that this control experiment ought to be made.

After a time a modification was made. The control experi-
ments were also tied in bags in order to make the two sets of
experiments alike in all points except for the application of
pollen. As the stigmas were often not ripe when the stamens
were cut out, later the bags round the control experiments were
untied, the stigmas were repollinated, and the bags retied.

Experiments also were made on a great number of plants to
see if self-pollination can take place if insects are excluded.
Flower buds of many plants were enclosed separately in muslin
bags.

Many of these experiments have been original investigations,
as sometimes neither teacher nor pupils knew what the results
would be and records of the pollination of the particular plants
chosen are not always to be found in books.

The pollination experiments that have been made every year
for more than thirty years thus fall into two classes:

POLLINATION EXPERIMENTS. CLIMBING PLANTS 61

1 . Experiments to see if pollen is necessary for the formation
of fruit in various plants.

2. Experiments to see if self-pollination can take place in
various plants in the absence of insects.

The following tables record the results of the pollination
experiments of twenty-one years :

JAMES ALLEN'S GIRLS' SCHOOL
SUMMARY OF POLLINATION EXPERIMENTS OF 2 1 YEARS

To see if pollen is necessary for the formation of fruit

Part I. CUTTING OUT THE STAMENS AND TYING THE BUDS IN BAGS

Plant

1. Bluebell

2. Buttercup

3. Eschscholtzia

4. Honesty

5. Stock

6. Toadflax

7. Snapdragon

8. Sea Campion

9. Canterbu

10. Foxglove

1 1 . Red Campion

12. Wallflower

13. Columbine

Part II. CUTTING OUT THE STAMENS, APPLYING POLLEN FROM
OTHER FLOWERS TO THE STIGMAS, AND TYING THE BUDS IN BAGS 1

jYb. ofexpts.

JVb. of fruits

Percentage of fruits

5

o

o

40

o

o

la ii

o

o

14
16

o

16

i
on
Bell

145
76
298

I
I
6

0-68
i'3

2-0

on

472
55

10

2

2'I

3-6

701
280

29

18

4'i
6-4

2,209

Plant

No. ofexpts.

No. of fruits

Percentage of fruits

i. Bluebell

26

26

IOO

2. Buttercup

69

69

100

3. Eschscholtzia

10

7

70

4. Honesty

J 7

17

IOO

'5. Stock

27

27

IOO

6. Toadflax

14

*3

92-8

7. Snapdragon

81

70

86-4

8, Sea Campion

78

57

73-0

9. Canterbury Bell

381

362

95'0

10. Foxglove

285

241

84'5

ii.

12. Wallflower

540

5'7

957

13. Columbine

264

251

95'0

1,792

1 Buds tied in bags only in later years.

62 THE BOTANY GARDENS

To see if self-pollination can take place in various /lowers in the absence

of insects

Percentage

Plant

No. ofexpts.

jVb. of fruits

of fruits

i. Broom

64

o

2. Foxglove

66

o

o

3. Yellow Iris

82

o

4. Tree Lupin

24

o

5. Monkshood

61

6. Pansy

69

o

7. Raspberry

25

o

8. Everlasting Pea

416

4

0-9

9. Scarlet Runner Bean

57

i

1-75

10. Yellow Toadflax

46

i

2'I

1 1 . Gorse

48

i

2'O

12. Anchusa

40

i

2'5

13. Adonis

8

8

IOO

14. French Bean

19

19

IOO

15. Eating Pea

112

112

IOO

1 6. Loganberry

109

107

98-1

17. Corncockle

40

39

97-5

1 8. Sweet Pea

5 1

49

96

19. Lychnis coronaria

97

93

95-8

20. Columbine

360

333

92-5

21. Poppy

5

77

9*5

22. Wallflower

126

113

89-6

23. Cheirantlms Allionii

TOO

62

62

24. Hollyhock

8 4

5i

60-7

25. Marsh Marigold

1 68

1 00 -]-2 small

60-7

26. Soapwort

43

17

39'5

27. Eschscholtzia

72

26

36-1

28. Nigella

3i7

1 15 good 2 8 poor

36-2 8-8

29. American Pillar Rose

49

ii

22'4

30. Snapdragon

1,288

259

20-1

31. Delphinium (perennial)

847

169

I9'9

32. Delphinium consolida

229

42

18-3

33. Strawberry

672

121

18

34. Figwort

74

10

i3'5

35. Canterbury Bell

98

5

5'i

36. Lupin

_65

3

4-6

6,111

At first no exact record of all the experiments made each
year was kept. Each girl described in her own book the experi-
ments she herself had made, and recorded her own results.

Later, the results of the experiments made by all the members
of the class that year were recorded by each girl, and, later still,
the summary of all the experiments of former years was given

POLLINATION EXPERIMENTS. CLIMBING PLANTS 63

to the class after the results of the year's experiments had been
fully discussed and noted.

The girls are often eager to take muslin and make bags at
home, so that more time can be spent in the lesson on actually
making experiments. Sometimes pins have been used instead of
cotton in making the bags and have been found satisfactory.

The pollination experiments, in particular, afford a training
in manipulation, in recording observations, in comparing the
results with those obtained by others, and in drawing conclu-
sions from a great number of facts.

There is now available for reference the results of thousands
of experiments in pollination made by the girls.

Sources of error in pollination experiments. The girls
who make the pollination experiments are young and have
had little experience in carrying out experiments. It is deli-
cate work cutting out stamens from small buds while on the
plants. They do the work unaided, though under supervision,
but the time allotted docs not permit of all the work being
examined.

It is possible that occasionally buds at a too advanced stage
have been taken. The most frequent source of error, however,
is that the muslin bags are not tied sufficiently tightly round
the buds. Experiments have been seen in which not only small
but large insects could crawl inside the bags.

Another source of error is the inclusion of more than one bud
in the bag. Even when apparently only one bud is enclosed,
if the growing point of the stem is included, more buds may be
formed after the original bud is enclosed.

When results are considered and compared in class reasons
for discrepancies are often suggested by the girls.

As a rule the girls feel their responsibility in helping to build
up records, and work well in the gardens.

Pollination in annuals and perennials. It has been noticed
that in some closely allied species experiments show that self-
pollination can take place in the annuals and not in the
perennials. The advantage to an annual of being self-fertile
is obvious.

Reference can be made to the experiments recorded on p. 62.

64 THE BOTANY GARDENS

Sweet Pea. Lathyrus odoratus. Annual.

96 per cent, formed fruit when insects were excluded.
Everlasting Pea. Lathyrus latifolius. Perennial.

0-9 per cent, formed fruit when insects were excluded.

Material for pollination experiments. The plants on which
pollination experiments are often made are grown in more than
one part of the garden, so as to give opportunity for many girls
at the same time to make experiments on the flowers. There are,
generally, paths on three sides of the pollination plots, sometimes
on four sides, and easy access to the plants is thus given. There
may be fifty or more girls making pollination experiments at
the same time in the garden.

POLLINATION OF PRIMROSE

Primroses do not seem to have a great attraction for bees even
when they arc growing near a hive. The bee-flies (Bombylids),
however, make many visits.

Darwin wrote several papers on the pollination of the prim-
rose, cowslip, and oxlip in 1861. He suggested that night-flying
moths pollinated the primrose. This theory has again been
brought forward in recent years, but has met with opposition.
As there have been such conflicting theories regarding the polli-
nation of the primrose it was decided in 1924 that experiments
should be made in the J.A.G.S. gardens.

Three wooden frames were made and covered with coarse
muslin. They were placed over clumps of primrose plants in the
early part of the year. The frames were 4 ft. 7 J in. long,
3 ft. 3 in. wide, and 2 ft. high, and there seemed plenty of air
inside them.

The muslin was not sufficiently near the plants to allow insects
to insert their proboscides through it to the flowers, as had been
seen in other experiments elsewhere.

One set of primrose plants was covered day and night, one
by day only, and one by night only.

There were unexpected delays in carrying out the experi-
ments. One difficulty was the time of placing the frame over
the plants which were to be exposed only at night. The school
is a day-school, and neither teachers nor pupils are at school
when the sun rises in March and April. Finally, the grounds-

POLLINATION EXPERIMENTS. CLIMBING PLANTS 65

man arranged to cover the night-exposed plants at 6 a.m. and
uncover the plants which were to be exposed in the day.

SUMMARY OF RESULTS OF EXPERIMENTS. 3 YEARS

Treatment

Plants

M.of
flowers
examined

A
B
G

Covered day
and night
Exposed by
night only
Exposed by
day only

Thrum-eyed "1
Pin-eyed J
Thrum-eyed
Pin-eyed
Thrum-eyed
Pin-eyed

1 02

140
117
241
262

M.of

fruits

Percentage

o

2 \

2-72

5/

214!

QI-O^

244J

The above experiments seem to show:

1. The primroses were not self-pollinated.

2. Night-flying insects played little part in the pollination of
these primroses.

3. Day-flying insects were the chief agents in pollination.

It is possible that, even in March and April, 6 a.m. is too
late an hour at which to cover the plants meant to be exposed
to night-flying insects only. In one of the years taken as an
example, the times of the rising of the sun were as follows:
April 4th 5.31, April i8th 4.59, April 3Oth 5.35 (summer time).

Experiments made in a fourth year were continued until a
late date (June 5th). The sun rose on May 3ist at 4.50 a.m.
(summer time). The number of fruits on the plants exposed
by night until 6 a.m. was much greater than in other years.
The results of all the experiments including those of the fourth
year were: percentage of fruits on plants covered by day and
night, o; on plants exposed by night until 6 a.m., 12-3; on plants
exposed only by day, 90-6.

The experiments on the pollination of the primrose are still
being carried on at J.A.G.S.

Mr. Marsden-Jones from direct and experimental evidence
concluded that day-flying insects do pollinate primroses effec-
tively, and that nocturnal insects (Lepidoptera) play no part
whatever in the pollination of the primrose. 1

Observation of visits of insects to flowers. Visits of insects
to flowers are a great source of interest. From very early days

1 Journal of the Linnean Society y Botany, December 1926.
4158 K

66 THE BOTANY GARDENS

classes went into the garden to watch insects visiting flowers.
The girls noted the kind of insect visiting the flower, the part
of the flower on which the insect alighted, the part of the insect
dusted with pollen, the number of flowers of the same species
visited by the same insect in one minute, and any other interest-
ing facts connected with pollination.

It was soon realized that the position of the nectary, when
present, had an important bearing on the pollination of the
flower: whether the nectar was easily accessible, whether the
insect in obtaining nectar received pollen, and if so, whether
the insect was likely to leave pollen on the stigma of the same
flower, or of the next flower of the same species visited. The time
of ripening of the stamens was often another important ob-
servation.

The classes in some years were large, containing more than
forty girls, and the time in the gardens was only half an hour.
Such classes were divided into small bands, each with a leader.

Most records of early observations were not kept, but some
arc available. The following were made in 1905-6 by 76 girls
working in divisions in the garden for one period of 30 minutes.

i. Visits of bees to 40 species:

Borage Meadow Rue

*Bramble Mint

Canterbury Bell *Monkshood

Clover Mullein

*Comfrey 'Nasturtium*

Dead-nettle, Purple Pansy

*Dead-nettle, White *Pentstemon

Figwort Poppy

Foxglove Radish

Funkia Runner Bean

Geranium (Pelargonium) Rose, Dog

Geranium, Wild (sp.) Salvia

Goat's Rue Sea Holly

Hogweed f Snapdragon

Hollyhock Speedwell

*Larkspur Sunflower

Lobelia Thistle

Lupin Vetch

Mallow ""Virginia Stock

Marigold Yellow Horned Poppy

Flowers seen visited by humble-bees, in some cases in addition to hive bees.
Only seen visited by humble-bees.

POLLINATION EXPERIMENTS. CLIMBING PLANTS 67

2. Visits of wasps to 20 species. Figwort was by far the most attractive
of these plants to wasps.

3. Visits of flies to 7 species.

4. Visit of moth to i species. Evening primrose (the girls leave school
in the afternoon).

The total number of species seen visited by insects in one
lesson of 30 minutes by 76 girls was 55. Individual girls often
described the visits of insects to 8, 9, or 10 plants of different
species.

Thirty-two girls watched bees visiting salvias in different parts
of the garden, 30 watched bees on hollyhocks, 20 watched bees
on poppies, 20 on 'nasturtiums', and 21 girls saw wasps visiting
figwort.

Flowers of same species visited by bees. Bees usually visit
the flowers of the same species as long as they can. Darwin
pointed this out in 1876 and stated that Aristotle had observed
the fact more than 2,000 years earlier. This habit enables the
bee to work more quickly. The advantage to the plant is
evident.

Number of flowers visited in one minute. Bees are great
workers, in fact they overwork. The life of a working bee is a
short one. Also they fly quickly. Darwin found that humble-
bees sometimes fly at the rate of ten miles an hour.

In the record quoted on pp. 66-7 of insects seen visiting
flowers at J.A.G.S., the number of flowers visited in one minute
was noted in each case. The following are some of the numbers:

JVo. of flowers

visited in

Insect Plant i minute

Bee Bramble 20

Dead-nettle (white) 19

Foxglove 1 2

Hollyhock 1 2

Larkspur 24

Marigold (heads) 30

'Nasturtium' 12

Pansy 15

Salvia 16

Virginia Stock 13

Wasp Figwort 22

68 THE BOTANY GARDENS

Species of insects visiting flowers. It is evident that a
greater number and greater variety of insects will visit 'open'
flowers with exposed nectar than irregular flowers with deeply
concealed nectar. More than sixty species of insects have been
noted visiting buttercup flowers. Miiller has shown that even
with apparently comparable 'flowers' (inflorescences) as those
of the Compositae and Umbelliferae the species of insects visit-
ing the flowers are different, the nectar being completely exposed
in the Umbelliferae, and slightly concealed in the corolla tube
of the florets in the Compositae.

Plant

No. of species
visiting flowers

Butterflies
and moth

Bees

Flies

Other
insects

Hogwccd
(Cow Parsnip)

118
Percentage

o

13
1 1

49
4i-5

56
47'5

Dandelion

93
Percentage

7
7'5

58

62-4

21
22'6

7
7'5

Provision of plants for insect visitors. It is well to have in
the garden the following plants if only to observe the visits of
insects to them: buttercup, broom, borage, dead-nettle, foxglove,
figwort, larkspur, gorse, monkshood, sweet pea, pinks, snap-
dragon, salvia. They can be grown in the 'order' beds, and in
other parts used for pollination experiments. It is a great
advantage to have clumps of them in different places, so that
many girls can be watching the visits of insects at the same time.

The most exciting plant to watch is salvia. When the bee
pushes its proboscis down the corolla to the nectar, and hits
the lower ends of the two anthers, the quick way in which the
upper ends swing roung and hit it on the back, leaving a patch
of pollen, is a constant joy to see.

The 'explosions' of pollen in broom and gorse are also popular >
and great interest is shown in the disappearance of the bee into
the snapdragon flower and its reappearance, with pollen on its
back, as it pushes opens the corolla and walks out backwards.
Borage and anchusa are also good 'bee plants'.

Provision of insect visitors for plants. At one time there
was a beehive in the garden, and girls had lessons in bee-keeping
after school, but the main reason for having the hive was that
there should be many bees visiting flowers.

POLLINATION EXPERIMENTS. CLIMBING PLANTS 69

FURTHER RECORDS OF INSECTS SEEN VISITING FLOWERS

(1927-30)

Number of Flowers at J.A.G.S. seen visited by

Bees . . .122 Wasps . . 14

Butterflies . . 34 Moths . . 5

Flies . . .24 Beetles . . i

Number of Flowers at J.A.G.S. seen visited by

1. Bees only . . . . . . 87

2. Bees and butterflies . . . . .10

3. Bees, butterflies, and flies .... 5

4. Bees, butterflies, and wasps .... 4

5. Bees and flies ...... 4

6. Bees, flies, and wasps ..... i

7. Bees and wasps ...... 7

8. Bees and moths ...... 3

9. Bees and beetles ..... i

10. Butterflies only . . . . . .11

11. Butterflies and flies ..... 3

12. Butterflies and moths ..... i

13. Flics only . . . . . . .11

14. Wasps only ...... 2

15. Moths only ...... i

Total . . . 151

RECORDS OF VISITS TO PLANTS OF TWO FAMILIES CHOSEN
FROM RECORDS OF VISITS TO PLANTS OF THIRTY-FIVE
FAMILIES

LEGUMINOSAE

J.A.G.S. Record *Knuth Record

i. Bees.

Broad Bean Humble Humble

Bird's-foot Trefoil Hive Hive Humble

Broom Hive Hive Humble

Clover red Humble Hive Humble

Clover white Hive Humble Hive Humble

Everlasting Pea Humble Humble

Gorse Hive Humble Hive Humble

Lupin Hive Humble Hive Humble

Tree Lupin Humble Humble

Melilot Hive Hive

Runner Bean Humble Humble

Sainfoin Hive Hive Humble

Sweet Pea Hive 'Bee'

Vetch Humble Hive Humble

Yellow Vetchling Hive Humble

* Knuth incorporated Miiller's records.

THE BOTANY GARDENS

J.A.G.S. Record

Knuth Record

2.

Butterflies.

Broad Bean
Lupin

Cabbage
4 Butterfly'

3-

Wasps.

Lupin

'Wasp'

4-

Flies.

Broom

Hover

GOMPOSITAE

i.

Bees.

Aster

Humble

Chicory
Coltsfoot

Hive
Hive

Cornflower

Hive Humble

Perennial Cornflower

Hive Humble

Daisy
Dahlia

Hive
Humble

Dandelion

'Bee'

Helenium

Hive

Knapweed
Marigold
Ox-eye Daisy
Sunflower

Humble
Hive
Humble
Humble

2.

Butterflies.

Autumnal Hawkbit

fFritillary
"^ Meadow Brown

Cornflower
Crepis
Dahlia

Cabbage
f Large White
\Blue
Small White

Knapweed
Marigold

J Large Heath
[Tortoise-shell
Large White

3-

Wasps.

Cornflower
White Daisy

'Wasp'
'Wasp'

4-

Flies.

Aster

Hover

Golden Rod
Ox-eye Daisy
Marigold
Wormwood

'Fly'
'Fly'
'Fly'
'Fly'

5-

Moths.

Carline Thistle

Burnet

Flies

Hive

Humble

Hive

Hive

Humble

Hive

Humble

Hive

Humble

Humble

Humble

Hive

Hive

Humble

Hive

Humble

Humble

Hive

Humble

fFritillary

|^ Meadow Brown, &c.
Blue sp.
f Small White
\Blue, &c.

fHeath sp.
\Tortoise-shell, &c.

Hover

Flies

Flies

Flies

Flies

2 Lepidoptera

POLLINATION EXPERIMENTS. CLIMBING PLANTS 71
CLIMBING PLANTS

The next addition to the botany gardens was a number of
climbing plants. In 1901 two screens, 6 ft. high, n ft. 6 in.
long, were made just outside the laboratory, one of trellis work,
and the other of wire-netting attached at intervals to wooden
uprights. Climbing plants were put on each side. It was found
better to have the plants near screens than near a wall, as girls
can stand each side of a screen, and make experiments or draw
the various climbing organs. The following were planted:
Clematis vitalb a ( traveller's joy), Clematis flammida, Clematis montana,
field bindweed, honeysuckle, hop (two plants), 'nasturtium',
Akebia, Bignonia, Dutchman's pipe, passion flower, scarlet runner
bean, and vine.

The plants were chosen so that different methods of climbing
could be studied; namely, by stems twining clockwise, by stems
twining anti-clockwise, by tendrils formed from stems and from
various parts of the leaf, and by hooks.

In 1915 another arrangement for climbing plants was made
elsewhere in the garden. The framework was constructed of
vertical and horizontal larch poles, to which other poles of
different diameters, driven into the ground at various angles
from the vertical, were nailed.

I. PLANTS CLIMBING BY TWINING STEMS

Rate of revolution.

Av. time

Plant

Direction
of twining

Locality

No. of
expts.

of I

revolution

Darwin's
results

hrs. min.

hrs. min.

Field Bindweed

Anti-clockwise

Garden

18

2 8

or Convolvulus

Hop

Clockwise

73

2 35

2 8*

2 31

Scarlet Runner

Anti-clockwise

Class-room

67

2 17

* 57

in green-
house

Scarlet Runner

Garden

38

2 37

* THE HOP. From seven observations on the hop plant made in April and
August, Darwin found that 'the average rate during hot weather and during the
day is 2 hrs. 8 min. for each revolution'.

From observations on an internode of a hop plant in a pot kept day and night in

72 THE BOTANY GARDENS

Scarlet runner bean. The observations made at J.A.G.S.
were on plants growing in the garden and also on plants in pots
indoors. The length of the longest lesson in which observations
were made was i hour 30 minutes, and in most years the lessons
were shorter than this. Continuous observation while the stem
of any of the above plants made a complete revolution was
impossible, and girls had to finish their observations in their
free time.

If they allowed some time to elapse between successive
observations there was a danger that the stem might have made
one or more complete revolutions in addition to a fraction of
one. To try to overcome this difficulty in the case of runner
beans, plants in pots with their stems supported by thin stakes
were put in the class-room, one plant for every pair of girls.
It was easier for girls in any free minutes between classes, or
before school, to note the position of the tip of the stem of a
plant in their room, than to go into the garden.

A piece of cotton, with a small weight at the end, held near
the tip of each stem, acted as a plumb-line. The pots were
placed on white paper, and, with the help of the plumb-line,
marks were made on the paper vertically below the stem tip.
The position of the tip was marked, at intervals, and the time
also was recorded.

2. Thickness of support. Pieces of cotton and string were tied
in a vertical position near convolvulus, Dutchman's pipe, and
hop, and the stems of these plants twined round them.

Ash poles of various diameters (sf , 3, 3!, 4, 4^ in.) were
driven into the ground near the hop plants on the original
screens. The hop stems twined round all the poles. It was not
easy to obtain ash, or other poles, of greater diameter than
4 in., and of practically the same diameter throughout the
length, so wooden cylinders were made 5 and 5 \ in. in diameter
and 30 ins. high. Hop stems were tied once against the bottom
of the cylinders. They just, and only just, climbed round the

Darwin's room when he was ill, Darwin found that 'the regular revolutions from
ninth to thirty-sixth inclusive were effected at the average rate of 2 hrs. 31 mins. 5 .
The movement was retarded on cold nights.

Speaking generally of plants climbing by twining stems Darwin stated that 'a
decrease in temperature always caused a considerable retardation in the rate of
revolution'.

POLLINATION EXPERIMENTS. CLIMBING PLANTS 73

cylinder the diameter of which was 5! in., and this was the
maximum thickness of the supports round which the hop stems
twined.

3. Angle of inclination of support. Before the new arrange-
ment for climbing plants was made, poles and sticks were put
in the ground near the original screens, at various angles from
the vertical, 30, 45, 60, 90.

Akebidy hop, and convolvulus twined round poles and sticks
at 45 from the vertical, but of the many climbing plants watched
only convolvulus and Akebia stems twined round horizontal
supports. 45 seems a critical angle in many cases.

4. Smoothness of support. Long glass rods were placed in
a vertical position near hop, Akebia, Dutchman's pipe, and con-
volvulus plants. The stems of all the plants twined round the
rods. The glass rods were then coated with paraffin wax, and
smooth brass vertical rods were placed near the plants. The
stems twined round all the vertical supports. As far as has been
tried the smoothness of the supports used has been no obstacle
to the twining of the stems.

5. Twisting of steins. The stems of twining plants become
twisted as they revolve. A good way of seeing this is to paint
a line along the convex side of the twining stem, and watch the
position of the line as the stem makes a complete revolution.

6. Effect of inversion of plants. Many runner bean plants
with their stems twining round wooden sticks have been in-
verted. The youngest part of the stem becomes unwound and
the tip twines in the opposite direction.

. 7. Effect of placing plants with twining stems on a clino-
stat. The stems of plants attached horizontally and rotated
slowly did not twine.

8. Effect of absence of light. The stems of runner beans and
other twining plants do not twine in the absence of light.

It has been pointed out that the cause of the contradictory
statements made by various experimenters has been the total
absence of light not being a condition of all the experiments. 1

1 Priestley, The New Phytologist, 1925.
4158 L

74 THE BOTANY GARDENS

The stems of plants which are only very faintly illuminated
may continue to climb.

At J.A.G.S. runner bean plants were put in the dark-room
in the part farthest from the door, a case of brown paper was
put over them, and the plants were never taken into the light
during the progress of the experiment. When light was needed,
a ruby lamp was used. The stems did not twine round the sticks.

II. PLANTS CLIMBING BY TENDRILS

Many experiments have been made at J.A.G.S. to test the
sensitiveness of tendrils of various plants on the screens, but
after 1909 there were better opportunities of making these
experiments in the lane. A record of some of the experiments
will be given in Chapter IX.

IX
THE LANE

IN 1909 the Governors made a special grant of ^10 for a lane.
A ditch and a hedgerow were made on each side of a grass
walk 8 ft. wide. The ditch was 2 ft. deep, 12 in. wide at the
bottom and at first 18 in. wide at the top, but afterwards it was
found necessary to make the sides more sloping. The soil for
the hedgerow was dug 2 spits deep, and the soil from the ditch
was added.

One hundred and twenty-five native shrubs, such as could be
found in country lanes, were planted. The greater part of the
hedgerow cpnsisted of hawthorns, beech, hedge maple, hazel,
holly, oak, with brambles, dog-roses, honeysuckle, traveller's
joy, and white bryony at intervals. It was soon found necessary
to put more soil in order to make a bank on which small plants
could grow.

It was some time before the lane looked like a real country
lane, but many girls took a great interest in it, and brought
primroses, violets, Jack-by-the-hedge, dead-nettles, stitchwort,
and other plants, and it has been for many years now an
especially favourite part of the garden in spring.

The lane at first was about 100 ft. long. It was lengthened in
1910, and again in 191 1, 1912, and 1914. The present length
is 1 63 ft.

The transect represents a vertical section of the lane with
typical plants growing in it (Fig. 29).

The youngest girls who learn botany usually have charge of
the lane. They prefer to work in pairs and have their own
special parts for which they are responsible. In lesson time the
same plants in spring, summer, autumn, and winter can be
studied, and when possible the whole plant is taken. In this
way a knowledge is gained of roots, underground stems, above-
ground stems, foliage leaves, flowers, fruits, seeds, and seedlings.
The lane is used by older girls also who carry out various experi-
ments described later.

The lane proved so useful, not only in lesson time, but as a
source of specimens, that it was decided in 1915 to make a

76 THE BOTANY GARDENS

considerable extension, but there was only sufficient space
available to make a hedgerow and ditch on one side in continua-
tion of the hedgerow and ditch of the first part. The part of
the lane added in 1915 was 150 ft. long. An additional 20 ft.

Hawthorn

Wild Rose

White Bryony
Hedge Bedslraw
-Foxglove

-FooTs Parsley

Ked Campion

Hedge Mushard
Lesser Celandine

Primrose
Germander Speedwell

Violer
Marsh Marigold

Deadneltle

Kibworr Plantain
Grass

Creeping
Bufrercup

^Dandelion

Forger-me-noh

FIG. 29. Transect of Hedge. James Allen's Girls' School.
(E. M. Delf).

has recently been made. Profiting by the experience gained
when the first part was made, the ditch was made deeper,
and wider at the top, and the sides were made to slope more
than those in the original lane. The shrubs and small trees are
the same species as those planted in 1909, with the addition of
wayfaring tree, gean, bird cherry, white beam.

Forty climbing plants were added: bramble, black bryony,
honeysuckle, traveller's joy, white bryony, wild rose.

Typical lane plants were put on the bank.

Growth of plants. After a time when the shrubs had grown
they were cut back every autumn. In country lanes 'hedging

THE LANE 77

and ditching' are usually necessary. Some of the plants on the
bank increased in number so much that many had to be up-
rooted. Coltsfoot, hogweed, and wild chervil, for example,
tended to crowd out smaller, more delicate plants.

At first the spindle trees were disappointing. Six had been
planted in the first part of the lane and three in the newer part,
but no fruit was seen for many years. It was ten years before
the beautiful fruits with their crimson walls and orange seed-
coverings did appear, and now the spindle trees in fruit in the
autumn are one of the features of the lane.

We heard from a horticultural firm that spindle trees do not
usually fruit until 10 or 12 years old, so those who have planted
them must not despair if the trees do not bear fruit at once.

CLIMBING PLANTS IN THE LANE

1. Twining plants. There are in the lane black bryony and
honeysuckle plants twining clockwise, woody nightshade twin-
ing indifferently, clockwise or anti-clockwise, and greater bind-
weed anti-clockwise.

Experiments on twining plants have been described in
Chapter VIII.

2. Scramblers. These are represented by bramble, cleavers,
and wild rose.

3. Tendril climbers. White bryony and traveller's joy have
been put in several parts of the lane. Experiments are often
made to test the sensitiveness of tendrils of various plants in the
lane and of those growing on the screens. The girls bring
watches and small clocks with seconds hands to the lesson.

i. The tendrils are rubbed and the time is noted before
curvature takes place.

The following table gives some results obtained one day in
the summer by a small class junior to the School Certificate class.

In these experiments the tendrils were just rubbed, the
number of strokes up and down were not counted. In later
experiments greater uniformity of treatment was introduced.
Three strokes were made, and the time was recorded before
the tendril changed from being straight I to curved P.

7 8

THE BOTANY GARDENS
SENSITIVENESS OF TENDRILS

Average time before

Plant

Locality

No. of expts.

coiling takes place

min. sec.

Clematis vitalba (Traveller's

On screen and

J 7

I 21

Joy)

in lane

Clematis flammula

On screen

7

24-6

Clematis montana

On screen

19

i 13

Everlasting Pea

Near screen

17

I 2

Passion Flower

On screen

17

54

White Bryony

In lane

'7

36

2. Very light objects, such as short pieces of cotton placed on
young tendrils, have also been used to cause curvature, and the
time has been noted before curvature took place. A long piece
of cotton was weighed in a chemical balance and measured
lengths were cut off and the weight was calculated. In one
set of experiments each piece of cotton weighed 0-0057 grn., and
the weight was sufficient to cause the tendrils of white bryony
and Clematis montana to coil. In another set pieces of cotton
weighing 0-113 m - an< ^ 0-208 gm. were used.

The results of some experiments made in one lesson are
given below:

RESPONSE TO WEIGHT OF PIECE OF COTTON

Weight of

Average time

each piece

No. of

before coiling

Plant

Locality

of cotton

expts.

took place

gm.

sec.

White Bryony

Lane

0-133

8

75

0*208

7

59

Everlasting Pea

Near screen

0-133

13

97

0-208

10

61

It is not claimed that the girls succeed in finding the exact
time that elapses in various plants between the application of
a stimulus and a curvature of a tendril, but it is an interesting
piece of work and gives new ideas on the sensitiveness of
tendrils.

Influence of aspect on time of flowering of plants. One side
of the lane has a southerly aspect, the other a northerly one.
Observations of the time of flowering of plants of the same

THE LANE 79

species are made. It is found there is generally a marked
difference, in some cases nearly a month.

Earlier flowering in successive years of plants on

Plant

side of lane with southerly aspect

days

days

days

days

Bluebell

18

8

4

9

Wild Chervil

16

2

7

9

Lesser Celandine

23

16

14

7

Pink Campion

5

6

5

Primrose

18

25

12

7

White Dead-nettle

9

30

30

Influence of aspect on soil temperatures. Two soil thermo-
meters were put in the lane, one (A) on the side with a southerly
aspect and one (B) on the side with a northerly aspect.

The following table gives a summary of readings taken during
four years.

READINGS OF THERMOMETERS IN SOIL ON THE TWO SIDES

No. of days on which
observations taken

Reading of A higher
than of B

Reading of A the
same as of D

Percentage

8 4

75 days

4 days

89-3
4-76

ANIMAL LIFE IN THE LANE

Lesson times are often spent out of doors studying various
animals in the lane. The lane affords facilities for the study of
the life-histories and habits of the common cross spider, lady-
birds, caterpillars, snails, bees, wasps, flies, and earthworms.
Birds have made their nests in the lane.

PLANTS OF THE LANE
SHRUBS AND SMALL TREES:

Beech

Bird Cherry
Blackthorn
Crab Apple
Dogwood
Gean
Hawthorn
Hazel

Fagus sylvatica
Prunus Padus
Prunus spinosa
Pyrus Mains
Cornus sanguined
Prunus avium
Crataegus Oxyacantha
Corylus Avellana

8o THE BOTANY GARDENS

SHRUBS AND SMALL TREES (continued) :

Hedge Maple Acer campestre

Holly Ilex Aquifolium

Oak Quercus robur

Service Tree Pyrus torminalis

Spindle Tree Euonymus europaeus

White Beam Pyrus aria

Willow Salix caprea

Yew Taxus baccata

CLIMBERS

Black Bryony Tamus communis

Bramble Rubus fruticosus

Bush Vetch Vicia septum

Clematis Clematis vitalba

Greater Bindweed CaJystegia sepium

Honeysuckle Lonicera Periclymcnum

Ivy Heeler a Helix

White Bryony Bryonia dioica

Wild Rose Rosa canina

Woody Nightshade Solanum Dulcamara

HERBS

Abundant Species

Bluebell Scilla non-scripta

Coltsfoot Tussilago Farfara

Creeping Buttercup Ranunculus repens

Germander Speedwell Veronica Chamaedrys

Ground Ivy Nepeta Glechoma

Jack-by-the~Hedgc Sisymbrium Alliaria

Primrose Primula vulgaris

Red Campion Lychnis dioica

Red Dead-nettle Lamium purpureum

Shepherd's Purse Capsella Bursa-pastoris

Thistle Carduus arvensis

Toadflax Linaria vulgaris

Violet Viola canina

White Dead-nettle Lamium album

Wild Chervil Anthriscus sylveslris

Wild Strawberry Fragaria vesca

Frequent Species

Angelica Angelica sylvestris

Burdock Arctium Lappa

Chickweed Stellaria media

Cinquefoil Potentilla reptans

Clover Trifolium repens

THE LANE 81

HERBS (continued):

Frequent Species (contd.)

Common Daisy Bellis perennis

Dandelion Taraxacum Dens-leonis

Dock Rumex Acetosa

Foxglove Digitalis purpurea

Greater Celandine Chelidonium majus

Hawkbit Leontodon hispidus

Hawkweed Hieracium vulgatum

Hedge Woundwort Stachys sylvatica

Hogweed Heradeum Sphondylium

Knapweed Centaur ea nigra

Lady's Smock Cardamine pratensis

Lesser Celandine Ranunculus Ficaria

Nipplewort Lapsana communis

Plantain Plantago lanceolata

Ragwort Senecio Jacobaea

Splashed Dead-nettle Lamium maculatum

Stinging Nettle Urtica dioica

Stitchwort Stellar la Holostea

Teasel Dipsacus sylveslris

Tufted Vetch Vicia Cracca

Wild Arum Arum maculatum

Yarrow Achillea Millefolium

Locally Abundant

Kingcup Caltha palustris

Occasional Species

Agrimony Agrimonia Eupatoria

Bladder Campion Silene Cucubalus

Dog's Mercury Mercurialis perennis

Figwort Scrophularia nodosa

Fleabane Pulicaria dysenterica

Herb Robert Geranium Robertianum

Mallow Malva sylvestris

Mullein Verbascum Thapsus

Periwinkle Vinca minor

Scentless Mayweed Matricaria inodora

Wood Sorrel Oxalis acetosella

Yellow Dead-nettle Lamium Galeobdolon

Rare Species

Early Purple Orchid Orchis mascula

4158 M

X

THE PONDS

AS long ago as 1902 efforts were made to have a pond in the
>** botany gardens, but difficulties arose, and permission was
not then given.

In 1903 a specially constructed tank was made for water
plants in the new botany laboratory. Miniature bogs were made
in the tank. Two trays, 4! in. deep, and perforated at the base,
were filled with peat. Each was supported on four legs and the
level of the trays was adjusted by screws so that the trays could
be touching the water, or out of the water.

In spite of the above arrangements the need for a pond in the
garden was still felt, and it was the first addition to the botany
gardens after the Board of Education grant in 1912 was given.

Construction of first pond. Inquiries were made and visits
were paid to various parks and gardens, and it was soon realized
that it was not advisable to have the pond lined with cement,
as in winter cement often cracks. The soil in most parts of the
botany gardens was stiff London clay, a fact that had often
been deplored, but in the construction of the pond the presence
of clay was an advantage.

The dimensions suggested for the pond were length 34 ft.,
width 23 ft. Soil was removed to the depth of 2 ft. 6 in. in the
middle, and the ground was sloped gradually up to the edge.
The clay in the middle of the pond was puddled and nothing
added, but on the sloping sides stiff clay from elsewhere was
put and well puddled.

The pond was made in 1913, and the puddled clay has stood
the test of time exceedingly well.

In order to prevent the water in the pond becoming stagnant
and offensive, water was brought in pipes from the nearest
source, and the supply regulated by two taps. One tap was
beneath the surface of the pond, and opposite to it was put a
hinged flap, edged with rubber, covering the entrance to a wide
outlet pipe. This arrangement was made so that when the tap
was turned and the flap put back there should be a current

THE PONDS 83

of water across the pond. The other tap was above the level of
the water, so that a hose could be fitted on it, and sprays of
water sent to sweeten the surface of the pond. It was high
enough to allow of cans being filled under it.

Some arrangement was necessary to deal with drainage from
the pond. There happened to be a soak-pit at a distance of
240 ft., and 'land drainage' was arranged for the greater part
of the distance: pipes were placed end to end but not connected.
In the neighbourhood of the pond, however, the pipes were
socketed. In many gardens the surplus water would not have
to be carried so far, and this item in the expense would be less.

This oval-shaped pond was surrounded by a grass verge, and
outside the verge a path of old York paving-stones 3 ft. wide.
By mistake the stones were cemented, and it was some time
before small plants established themselves between them.

Four beds roughly triangular in shape were made near the
pond.

Freshwater marshes were made in two of the beds. The
whole water garden is at a much lower level than the adjoining
part, and when rain falls water flows down the banks into the
freshwater marshes and the pond. When there is not sufficient
rain to keep the soil of the freshwater marshes wet the tap under
the surface of the water can be turned on; the water from the
pond then overflows and some goes into the adjacent parts.
Sometimes in dry weather a hose is fitted on the tap above the
pond and connected with a sprinkler, and the soil in the fresh-
water marshes is thus kept wet.

The soil to the depth of 12 in. was taken away from the other
two beds. In one of these beds soil from a salt marsh on the
east coast was put (see Chapter XII). The fourth bed near the
pond was planned to represent a peat bog and peat bought from
a horticultural firm was put in it.

Estimates for the whole of the above work were submitted
by various firms, but some horticultural firms did not wish to
undertake the work without supplying the plants, and finally
an estimate from a local builder was accepted, and navvies did
the work, the construction of the pond being always under the
supervision of the botany department.

The cost of the construction, exclusive of stand-pipe and tap

84 THE BOTANY GARDENS

for hose, was 27.* This did not include the removal of
excavated soil. After the pond was made it was found advisable
to have some stone steps in the bank leading down to the pond.
The cost of the steps was i.

In planning the pond we were greatly helped by Mr. Hales,
Curator of the Chelsea Physic Gardens.

Construction of the small pond. As the bigger plants grew
and increased in number in the pond they crowded out small

Marsh
Mangold

Yellow

Water
Plantain

Purple
Loosestrife

Horse-
rail

, ..._.J's ^|AH^ - "

Floafing Pondweed Tail

FIG. 30. Transect of Pond. James Allen's Girls' School.
(E. M. Delf)

plants such as frogbit, milfoil, and water violet. In 1917 an
attempt was made to reserve a place for the smaller plants. On
one side of the pond an enclosure was made. Wire-netting
(mesh -| in.), supported by iron pipes, was extended from the
bottom of the pond to the surface of the water, and touched the
edge of the pond in two places. Many plants, such as 'bulrushes'
and Sparganium, were removed from the enclosure thus made.

Small water plants were put in the part enclosed by the wire-
netting and flourished for a time. But gradually the big plants
encroached. Some plants, as water-lilies, sent stems under the
ground, thus avoiding the wire-netting, and made new plants in
the 'bay' or enclosure. In a few years in spite of pulling up
hundreds of Sparganium plants, bulrushes, and reeds, the 'bay'
was choked with big plants.

In 1921 it was decided to make a smaller pond and not have
in it any of the larger plants that had at times almost choked

1 Cost of stand-pipe and tap for hose was i.

THE PONDS 85

the big pond. It was arranged that the new pond should be
near the first pond so that the same water-supply would be
available and the same drainage. In planning the new pond
the presence of big hawthorn bushes complicated matters, as
it was not wished to cut them down. Finally, it was decided
to make the pond of a horseshoe shape and allow a piece of land
to jut into it (see frontispiece) .

Puddled clay was used, as in making the bigger pond, but
the expense was increased by the drought of 1921 occurring
when the clay had been puddled, and no water was allowed
to go into the pond. Finally, the water authorities gave permis-
sion for the pond to be filled. But by this time some of the clay
had dried so much that it had to be replaced.

It was desired to have a stone path round the second pond,
but the price of paving-stones had increased so much that it
was out of the question.

After the pond had been made the sloping grass between the
two ponds was found so slippery after rain that a stone path with
steps was made. This time it was seen that the 'joints' between
the stones were open and not cemented.

SUBMERGED PLANTS*

Canadian Water Weed Elodea canadensis

Hornwort Ceratophyllum demersum

Pondweed, Curly Potamogeton crispus

Pondweed, Shining Potamogeton lucens

Water Soldier (winter) Stratiotes aloides

Water Violet Hottonia palustris

PARTLY SUBMERGED PLANTS*

Frogbit Hydrocharis morsus-ranae

Limnanth, Common Limnanthemum nymphaeoides

Mare's Tail Hippuris vulgaris

Pondweed, Floating Potamogeton natans

Water Crowfoot Ranunculus aquatilis

Water-lily, White Nymphaea alba

Water-lily, Yellow Nuphar luteum

Water Milfoil Myriophyllum vulgatum

Water Persicaria Polygonum amphibiwn

Water Plantain, Floating Alisma natans

Water Starwort Callitriche verna

Water Soldier (summer) Stratiotes aloides

* In most water plants the flowers open above the surface of the water.

86

THE BOTANY GARDENS
MARGINAL PLANTS

Arrowhead

Bog Bean
*Brooklime

Bulrush (True)

Branched Bur-reed

Codlins and Cream

Flowering Rush

Gipsywort
*Horsetail
*Iris, Yellow
*Marsh Marigold

Marshwort, Procumbent

Musk
*Meadow-sweet

Pickerel Weed
* Purple Loosestrife
*Reed, Common

Reed Mace, Great
*Rush, Common

Scirpus, Creeping

Skullcap, Greater
*Spearwort, Greater
*Speedwell, Marsh

Speedwell, Water

Sweet Flag
*Umbrella Plant

Water Dock, Great
*Water Mint

Water Forget-me-not

Water Plantain

Sagittaria sagittifolia
Menyanthes trifoliata
Veronica Beccabunga
Scirpus lacustris
Sparganium ramosum
Epilobium hirsutum
Butomus umbellatus
Lycopus europaeus
Equisetum maximum
Iris Pseudacorus
Caltha palustris
Apium nodiflorum
Mimulus luleus
Spiraea Ulmaria
Ponlederia
Lythrum Salicaria
Phragmites communis
Typha latifolia
Juncus communis
Scirpus palustris
Scutellaria galericulata
Ranunculus Lingua
Veronica scutellata
Veronica Anagallis
Acorus Calamus
Cyperus longus
Rumex Hydrolapathum
Mentha aquatica
Myosotis palustris
Alisma Plantago

* Growing also in freshwater marshes.
PLANTS OF FRESHWATER MARSHES

Plants marked * in list of Marginal
Alder

Bistort, Snake's
Brook -weed
Creeping Jenny
Globe Flower
Golden Saxifrage
Marsh Bedstraw
Marsh Cinquefoil
Marsh Gentian
Marsh Orchid
Marsh Pea Vetchling
Marsh Pennywort

Plants and

Alnus glutinosa
Polygonum Bistorta
Samolus Valerandi
Lysimachia Nummularia
Trollius europaeus
Chrysosplenium oppositifolium
Galium palustre
Potentilla palustris
Gentiana Pneumonanthe
Orchis latifolia
Lathyrus palustris
Hydrocotyle vulgar is

THE PONDS 87

Meadow Rue Thalictrum flavum

Ragged Robin Lychnis Flos-cuculi

Royal Fern Osmunda regalis

Rush, Twisted Juncus spiralis

Sedge, Pendulous Carex pendula

Spearwort, Lesser Ranunculus Flammula

Water Avens Geum rivale

Water Parsnip Slum angustifolium

Yellow Loosestrife Lysimachia vulgaris

PLANTS OF THE SALT MARSH

The soil from the salt marsh on the east coast consisted of
sods containing the following characteristic plants :

Marsh Samphire Salicornia herbacea

Sea Lavender Statice Limonium

Sea Manna Grass Glyceria maritima

Sea X)rache Atriplex portulacoides

Additional plants were obtained from other salt marshes (see
Chap. XII). The plants were watered with salt solution.

THE PEAT BOG

The plants did not thrive at first in the peat bog near the
pond and in 1918 the bog was re-made.

1 . The peat that had been obtained from a horticultural firm
was removed.

2. Stiff clay was put on the bottom and sides of the bed and
was well puddled.

3. Peat from a bog in Lancashire was placed in the bed.

It was felt that the hard London water was not good for bog
plants and rain water was used in watering the plants.

Plants characteristic of peat bogs, such as sundew and bog
pimpernel, thrived after the above alterations had been made.

For the list of plants growing in the peat bogs see Chapter XL

COLONIZATION OF STONE PATH

The following planted themselves in the crevices in the stone
path round the pond.

Bittercress Gipsywort Meadow Buttercup

Clover Grass, Meadow Meadow-sweet

Daisies Iris, Yellow Plantain

FooFs Parsley Marsh Marigold Purple Loosestrife

Forget-me-not Marsh Pennywort

88 THE BOTANY GARDENS

Later many of these were replaced by prostrate plants such
as species of thyme, sandwort, &c.

REPRODUCTION IN WATER PLANTS

It has already been shown that difficulties arose in the bigger
pond owing to the rapid increase in numbers of some of the
plants. Clearings have to be made at intervals, or the pond
would become choked. Various methods have been tried. The
most successful has been to put on wading boots, go into the
pond, and pull up the superfluous plants by their underground
or undcr-watcr stems, which in most cases connect numbers
of plants. The plants thus removed are often most useful in the
laboratory, every member of a class being able to have a plant
when studying its structure and drawing it. The surplus algae,
and other small floating plants, near the edge of the pond are
removed by hand, and those farther in the pond by rakes with
long handles, such as hay rakes. An 'umbrella plant 5 (Cyperus
longus] of which another name is 'galingalc', unfortunately put
in the pond, not only made many plants where it was planted
at the edge of the pond, but numbers of plants appeared in the
freshwater marsh 33 ft. away, and in the 'order' beds at a dis-
tance of 74 ft. At last it was decided to remove the original
plant, but such a big hole had to be made in the bank of the
pond when the plant was taken out, that a man stood by with
puddled clay and filled in the gap immediately cost 14^.

The multiplication of plants in the freshwater marshes also has
been great. Eight yellow iris plants were put in the freshwater
marshes in 1913. Five years after, 201 iris plants were removed
from one marsh alone in one morning and numbers were left.

The great increase in numbers of plants in the ponds and
marshes has its advantages as well as its drawbacks. Yellow iris
plants are valued not only on account of their beauty, but for
their usefulness when pollination experiments are being made.

The number of purple loosestrife plants was originally only
two, but hundreds have appeared in the freshwater marshes
and round the edges of the pond, greatly adding to the beauty
of the water garden which is such a marked feature of the
botany gardens in June and July.

When the small pond was made not a single water plantain
was put in it but scores soon appeared. It is thought that seeds

THE PONDS 89

may have been borne by the water that came from the big pond
into the little, or possibly have been introduced with other
plants.

Three greater spearwort plants were put in the new pond.
Those in the old pond had not increased greatly in number, but
in the new pond they increased so rapidly that numbers had
to be removed and still they are a danger. The flowers are so
large and beautiful it seems a pity to take out the plants but it
has to be done.

These details are given so that others may profit by our experi-
ence. Better ponds could be made now at Dulwich when so
much experience has been gained.

Plants to be avoided when stocking a pond:

Branched Bur-reed

Common Reed

'Bulrush 5 (Reed Mace)

'Umbrella Plant' (Galingalc)

Water Dock.

SOME RECORDS OF REPRODUCTION IN WATER
AND MARSH PLANTS

Name of plant

Number planted \ Number removed

Period

years

Branched Bur-reed

2

4,987

15

Bulrush

i

59

9

Common Reed

i

1,369

9

Reed Mace (often called

6

127

13

Bulrush)

'Umbrella Plant'

i

650

4

Water Plantain

None in small

92

3

pond

Greater Spearwort

3

1,285

6

*Horsetail

6

457

5

Pendulous Sedge

1,974

Purple Loosestrife

2

{None removed
271 plants

13

Soft Rush

I

3 1 4 clumps

4

Yellow Iris

8

865

6

* Numbers removed not counted for some years.
SOME CONDITIONS UNDER WHICH WATER PLANTS LIVE

Comparison of temperatures of water in pond and air
outside pond. A thermometer registering maximum and mini-

4158 N

go THE BOTANY GARDENS

mum temperatures was fastened under the water in the large
pond, and a similar thermometer was placed in the air outside
the pond on a branch of a tree nearly above the submerged one.
Readings of the thermometers were, and are still being taken,
in and out of school hours by various girls in the class studying
water plants. Readings are rarely taken in the holidays. Frost,
for varying periods in three years, prevented readings of the
thermometer in the pond being noted. (In one year the pond
was frozen for twenty-four consecutive days, and when the ice
melted the thermometer was found to be broken.)

RECORDS OF TEMPERATURE OF WATER IN POND (A) AND AIR
OUTSIDE POND (B)

Mo. of days on

Mo. of days on

Mo. of days on

which max. temp.

which min. temp.

which readings

of A lower than

Percent-

of A higher than

Percent-

taken

that of B

age

that ofB

age

i si year

65

62

95'4

62

95'4

7 years

250

233

93'2

242

96-8

12 years

440

408

92'7

386

87-7

The readings of the maximum and minimum thermometers
in the pond and in the air outside the pond taken during (i)
July of one year, and (2) June of another year were as follows:

Maximum

temperature

Minimum

temperature

Date

In pond

In air outside

In pond

In air outside

F.

F.

F.

F.

(i) July i

79

9

60

54

2

76

8 4

57

47

3

80

8?

58

49

4

84

9 1

60

5i

7

78

85

61

49

8

76

88

57

48

9

79

84

60

52

10

79

84

61

5i

ii

77

81

58

55

14

81

9

64

55

J5

85

88

65

57

16

79

84

61

54

1 7

76

82

58

52

18

80

89

61

54

No. of days on which readings were taken =14

,, ,, ,, max. temp, lower in pond =14
,, min. temp, higher in pond = 14.

THE PONDS

Date

Maximum temperature

Minimum temperature

In pond

In air outside

In pond

In air outside

(2) June 7

69*

72

57

48*

9

60

67

60

55

12

71

80

56

46

13

69

78

56

48

'4

67

76

52

44

15

64

76

54

47

19

79

88

55

49

20

68

80

58

52

21

70

79

54

47

22

61

68

60

54

23

60

69

56

48

26

60

69-5

58

52

29

64

70

58

5 1

30

62

7i

55

49

No. of days on which readings were taken = 14

,, ,, ,, max. temp, lower in pond =14
,, ,, ,, min. temp, higher in pond = 14

SUMMARY OF READINGS OF MAXIMUM AND MINIMUM
THERMOMETERS IN MAY

No. of days on which readings were taken = 16

,, max. temp, lower in pond = 16
,, ,, min. temp, higher in pond = 16

The above readings show that generally the maximum tem-
perature of the water is lower than that of the air above it and
:he minimum temperature higher, that is the temperature of
:he water does not show such extremes of temperature as the
dr. The girls see that water plants live under more uniform
:onditions of temperature than land plants.

The beauty of the ponds and marshes. In the summer the
ponds are not only interesting to biologists, but attractive to
ill on account of their great beauty. The water-lilies, water
;oldiers, and water plantains in flower in the deeper part, the
wealth of colour afforded by the purple loosestrife, yellow loose-
;trife, and meadow-sweet, and the background of royal ferns,
Bulrushes, and reeds, make a picture not easily forgotten.

ANIMALS OF THE POND

The ponds are as valuable for the study of animals as for the
;tudy of plants. In the ponds and marshes are numbers of frogs,

92 THE BOTANY GARDENS

toads, newts, pond skaters, water boatmen, great water beetles,
pond snails (trumpet and spiral), sticklebacks, water fleas, fresh-
water shrimps, caddis fly larvae, and larvae of dragon flies. With
the exception of some water snails put in the pond in 1913
for the purpose of checking the growth of algae, and two newts
in the same year, no animals have been put in the pond. They
have come in by themselves.

Probably the eggs of some have been introduced on the leaves
of plants. Frogs and toads often pay visits to a pond from a
distance. In the winter in the J.A.G.S. pond, as in other ponds,
frogs bury themselves in the mud at the bottom. Water boat-
men, pond skaters, and great water beetles can come from afar,
as sometimes at night they rise from the pond in which they have
been living, and fly to another pond and settle there.

The above animals are the regular inhabitants of the pond.
There are occasional visitors. In 1924, just before the holidays,
a pair of wild ducks appeared on the big pond. On the first
day of the next term the duck was seen with seven ducklings.
After a time the parent ducks flew away, but nearly every year
a pair come to stay for a time on the ponds and marshes.

In the spring the pond seems absolutely full of frogs and frog
spawn and afterwards tadpoles. Later, tiny frogs can be seen
leaving the pond, and some are met at a considerable distance
making their way to yet more distant parts.

With ponds so accessible it is easy for girls to study the life-
histories of animals. It is fascinating to watch the various pond
animals, and girls have been enthralled at actually seeing the
metamorphosis of dragon flies.

To-day I saw the dragon fly

Gome from the wells where he did lie,

An inner impulse rent the veil

Of his old husk: from head to tail

Came out clear plates of sapphire mail.

He dried his wings; like gauze they grew;

Thro' crofts and pastures wet with dew,

A living flash of light he flew. TENNYSON.

XI
THE HEATH AND THE BOG IN THE HEATH

THE HEATH

E soil in two small pieces of ground, each about 12 ft.
-L by 5 ft., was trenched in 1905, some was taken away and
soil from a heath put in its place.

Typical heath plants such as heather, fine-leaved heath, and
sheep's fescue grass grew well in the heath soil. These plots were
convenient as they were just outside the laboratory, and for nine
years heath plants were studied in them; but they were very
small. In 1912 a piece of ground 100 ft. long, 40 ft. broad at
one end and 24 at the other, was set aside for a heath in the new
field. The ground was trenched two spits deep in 1914, the
grass was buried at the bottom, and the subsoil was kept in its
original position. The cost of the above work was fy i$s. Soil
was brought from a heath in Surrey. The cost (carriage in
eluded) in 1914 was i a load. In 1933 it was i los. a load.
The roots of heather and heath plants are invaded by fungal
threads, the association between the roots and the fungus being
called a mycorrhiza. Cells of the root digest the hyphae.
Seedlings of heather and heath do not develop properly unless
the fungus is present. This shows why it is so important to have
soil from a heath when trying to grow heather and other heath
plants.

SUPPLY OF PLANTS

The following were ordered from a plant nursery near a
heath:

200 heather plants
100 fine-leaved heath plants
200 whortleberry plants.
100 bramble plants
100 gorse plants
24 yarrow plants.

Some of the plants were delayed on the railway owing to the
war, and arrived in a bad condition. Few of the gorse plants
lived. The number of plants supplied the first year seemed

94 THE BOTANY GARDENS

large, but it was quite inadequate to populate the heath.
Nearly every year since the heath was made, typical heath plants
from various parts of the country have been put in it. At one
time parts of the heath represented heaths in different regions
of Britain. The plants had come from a Yorkshire heath, two
Kent heaths, and two heaths in Scotland. The year after the
soil was brought typical heath plants appeared which had not
been planted, so presumably the seeds were in the soil. The
plants (tormentil, sheep's fescue grass, and heath bedstraw)
appeared in groups.

Gorse. It was found more satisfactory to sow gorse seeds in
pots and put out the young plants, than to transfer larger plants.
When the gorse was established many young seedlings were
found. After a time the gorse bushes had to be cut back.

Bracken. For many years there had been difficulty in trans-
planting bracken. The plants often died. The advice of a
Director of a well-known park was to take a yard of soil with
each plant. Bracken plants were given to the school from the
park, but it was necessary to send a cart as so much soil was
removed with the plants. The plants lived.

Bramble. At first bramble was kind in covering bare places,
but it grew so rapidly it had to be cut back in 1917, 1919, 1920,
and other years.

Heath grasses. Plants not characteristic of heaths had to be
removed, and often bare patches were left. Seed of typical heath
grasses (sheep's fescue and wavy hair grass) was obtained from
a firm specializing in grasses, and sown. The result was most
satisfactory.

Heather. Heather is not easy to transplant but plants can be
grown from cuttings.

Struggle of heath plants with aliens. Meadow and couch
grass at first were great foes and a few months after the heath
was made the heath plants were almost choked by them.

As in the case of the wood, girls of other forms came to the
rescue of those in charge, and by the end of the first year the

THE HEATH AND THE BOG IN THE HEATH 95

heath seemed clear of these grasses. But it was only clear for
a time and there was a constant battle for many years.

During the first year also, a struggle with groundsel occurred
but the groundsel was more easily exterminated. Creeping
buttercup, clover, dock, and thistles were other troublesome
weeds until the heath plants were well established, but they
were not so persistent as the grasses.

Transpiration in heath, moorland, and bog plants. For

many years it was believed that heath, moorland, and bog
plants had restricted transpiration, not on account of the
scarcity of water, but because the water contained toxins, or
poisons.

Schimper, in 1898, when considering the small leaves and
protected stomates seen in many heath and bog plants, charac-
ters usually associated with plants which have restricted trans-
piration, concluded that these plants lived under conditions of
'physiological drought': that toxins were present in the soil.
This theory held sway for years. In 1918 Montford showed by
work on cotton grass that there was no 'physiological drought'
in a bog. He showed by experiments that the water of moorland
soils was not poisonous to moorland plants, and that absorption
and transpiration of water go on freely. 1

In 1923 Stocker found that, although individual leaves in
heather and cross-leaved heath are small, the plants have not
a reduced leaf area in relation to the absorbing surface of the
roots, that transpiration is not restricted, and that the plants do
not live under conditions of 'physiological drought'.

PLANTS OF THE J.A.G.S. HEATH

Dominant Heather Calluna vulgaris

Dominant Fine-leaved heath Erica cinerea

Bramble Rubus fruticosus

Bracken Pteris aquilina

Wavy Hair Grass Deschampsia flexuosa

Sheep's Fescue Grass Festuca ovina

Broom Cytisus scoparius

Gorse Ulex europaeus

Yarrow Achillea millefolium

Whortleberry Vaccinium Myrtillus

1 See also Chapter XII. Dr. Delf 's work on Transpiration in Salt Marsh plants.

96 THE BOTANY GARDENS

Wood Sage Teucrium Scorodonia

Harebell Campanula rotundifolia

Tormentil Potentilla Tormentilla

Mountain groundsel Senecio sylvaticus

Eyebright Euphrasia qfficinalis

Bird's-foot Trefoil Lotus corniculatus

Devil's Bit Scabious Scabiosa succisa

Hair Moss Polytrichum

Sheep's Sorrel Rumex Acetosella

Club Moss Lycopodium clavatum

Cornish Heath Erica vagans

Heath Bedstraw Galium saxatile

Bilberry Empetrum nigrurn

Milkwort Polygala vulgaris

Sheep's Bit Jasione montana

Bent-grass Agrostis canina

Lady's Tresses Spiranthes spiralis

Ciliated Heath Erica ciliaris

St. Dabeoc's Heath Dabeocia polifolia

St. Keverne Heath Erica vagans. var. St. Keverne
Mackay's Heath, Crawford's Erica Mackayi. Jlore pleno
variety

THE BOG

It was decided in 1916 to have, in the heath, a bog much
bigger than the one near the pond. The contour of the heath
showed a natural basin-like shallow depression near the middle,
towards the back. This depression was made deeper, and a
narrow part 4! ft. wide was made running into it from the
front. To prevent the water draining away, when the hollow
and narrow part were filled with peat, the bottom and sides
were lined with puddled clay.

An estimate for preparing the ground for the new bog and
redigging and repuddling the small bog was 3 13,5-. od. It
was accepted.

When the soil was taken away the precious top spit was spread
over other parts of the heath.

Provision of peat. Peat straight from a peat bog was thought
to be the most satisfactory way of obtaining it. Professor
Bottomley, who was at the time conducting experiments on
peat, kindly promised that some from a bog in Lancashire
should be sent free, except for the expense of labour (digging
the peat and packing it in sacks) and carriage.

THE HEATH AND THE BOG IN THE HEATH 97

The area of the big and little bogs is 234 square ft., and it

was first arranged that that extent of peat should be dug from

a depth of 2 ft., but, on account of expense, it was altered to

a depth of i| ft.

Samples of peat were sent. On December 8th, 1916, an order
for 6^ tons of peat from the Sphagnum patches of the bog was
given, but it did not come for seven months. The delay had
been caused by the peat having been frozen for two months,
by shortage of railway wagons, and by difficulty of obtaining
labour. The peat arrived in July 1917 and proved to be
cotton grass peat as well as Sphagnum. It was put in the two
places prepared for it.

After the big bog was made, the soil round it, which had
suffered while the bog was being made, was trenched, and
2 1 loads of heath soil were added to it.

Water for the bog. In case there should not be sufficient rain
at any time to keep the peat wet, water is brought in a pipe to a
part of the heath near the bog, and the bog can be flooded by
a hose. Unfortunately it is not possible to use rain-water for
the whole bog. Plants newly put in arc sometimes watered
with rain-water to give them a good start.

Plants of the bog. Bog plants, with the exception of Sphag-
num, thrived in the new bog. Cross-leaved heath formed con-
spicuous patches, bog myrtle grew well, creeping willow, pistil-
late and staminate, soon flowered, bog pennywort spread
rapidly. Cotton grass also flourished and when in fruit, with
its nodding white plumes, gave a characteristic look to the bog.
Grass of Parnassus flowered, sundews lived and in one year
survived the winter, four butterworts also lived through a winter
and three seedlings were found.

Sphagnum., sent from various bogs in England and Scotland,
has never been grown successfully at Dulwich. Year after year
it has been planted. Sometimes it has been put right in the
peat, at other times it has been put in a dish and the dish put
in the peat. It has been kept wet with rain-water but it has
never formed a sheet.

Thinning of plants. The rushes spread very quickly and
after a time so many plants had to be removed that the roots

4158 o

9 8 THE BOTANY GARDENS

of those taken up were washed to save the peat. Cotton grass
also had to be removed and hundreds of marsh pennywort
plants. The willows were cut back.

PLANTS OF THE
Cross-leaved Heath
Marsh Pennywort
Bog Myrtle
Blue Moor Grass
Bent Grass
Cotton Grass
Heath Rush
Soft Rush

Sharp-flowered Jointed Rush
Lesser Jointed Rush
Sedges

Bog Asphodel
Creeping Willow
Lesser Spearwort
Marsh Bird's-foot Trefoil
Bog Moss
Bog Pimpernel
Marsh St. John's Wort
Marsh Andromeda
Sundew, Round-leaved
Sundew, Long-leaved
Sundew, Intermediate
Butterwort, Common
Butterwort, Large-flowered
Grass of Parnassus
Bog Gentian
Marsh Red Rattle
Marsh Club-moss

J.A.G.S. BOGS

Erica tetralix
Hydrocotyle vulgaris
Myrica Gale
Molinia caerulea
Agrostis canina
Eriophorum vaginatum
Juncus squarrosus
Juncus effusus
Juncus acutiflorus
Juncus supinus
Car ex sp.

Narthecium ossifragum
Salix repens and $
Ranunculus flammula
Lotus uliginosus
Sphagnum compactum
Anagallis tenella
Hypericum elodes
Andromeda polifolia
Drosera rotundifolia
Drosera longifolia
Drosera intermedia
Pinguicula vulgaris
Pinguicula grandijlora
Parnassia palustris
Gentiana Pneumonanthe
Pedicularis palustris
Lycopodium inundatum

XII
SAND DUNES SALT MARSHES PEBBLE BEACH

SAND DUNES

THE first sand dune in the botany gardens was made in 1907.
The sand was sent from Lowestoft by the Great Eastern
Railway. A number of typical plants from sand dunes thrived
in it, and it proved very useful, but the dune was a very small
one, and when more land was available for botany gardens it
was decided that, among other things, a larger sand dune
should be made.

In 1919 it was found that sea sand could not be obtained in
the same way as before, and many inquiries were made else-
where. The chief difficulty was the delivery at the school. The
railways would convey it to London, but the goods depots were
usually some way from Dulwich, and the cartage would add
considerably to the cost. However, after seeing a sample from
Brighton, it was agreed that the sand should be sent to East
Dulwich station. The school authorities had it carted from the
station.

Cost. The price of the sand steadily increased as the years
went on. In 1915 it was 55*. rorf. a ton delivered at East
Dulwich, in 1919 &r. 3^., in 1920 lOj*. 6rf., in 1923 us. iorf., and
in 1933 the price was 12^. $d.

The length of the piece of ground allotted to the new sand
dune was 31 ft., and the width 23 ft. at one end and 18 ft. at
the other end. In January 1920, 7^ tons of sand were put on the
site, and spread over the ground. The amount of sand seemed
so inadequate that 6 more tons were obtained, and then 9 tons,
making a total of more than 22 tons. The last consignment of
sand was piled up in places to imitate dunes.

In 1923 the sand dune was enlarged and 8 additional tons of
sand were put on it.

During the first year of the dune (1920) various plants,
such as sand sedge, sand lyme grass, sea holly, sea stork's bill,
viper's bugloss, and biting stonecrop, were put in it, and thrived.
Other plants, such as groundsel, yarrow, and toadflax, not

ioo THE BOTANY GARDENS

characteristic of sand dunes, thrived also, and when uprooted

were found to have unusually long roots.

In 1921 one buck's-horn plantain appeared, and by means of
seeds gave rise to many new plants. In 1922, 6,614 plantain
plants were removed, and in three years a total of 12,563.

The rate of reproduction of sand sedge was even more rapid.
By design only one sand sedge plant, planted in 1920, was
allowed to develop, so that the rate of reproduction could be
noted. The one plant gave rise to so many other plants, that, in
four years, more than 22,000 were removed, and about 7,000
were still left in the dune.

The process of colonization was clearly seen. From the one
original sand sedge plant straight rows of other plants appeared,
and steadily grew in length, appearing like columns invading
a territory. The photograph (Fig. 32) taken in 1922 shows the
radiating appearance, but it would have shown even better if
the photograph had been taken a little sooner.

Under the surface was a network of rhizomes, which helped
to bind the layers of the sand, especially those near the top. In
7 years, 72,300 plants were removed, and still great numbers
were left. No girl who looked after the sand dune will easily
forget that sand sedge is reproduced by other means than
seeds.

The figures for reproduction in sand lyme grass seem insigni-
ficant after those of sand sedge. From one plant put in the dune
in 1920 more than 3,000 descendants were removed in 5 years,
and 329 remained in the dune.

The sand dune soon began to look like a normal sand dune.
Viper's bugloss and sea holly quickly increased by means of
seeds; there was one viper's bugloss plant in 1920 and 60 plants
in 1925. The long roots of viper's bugloss (10 in. long in the
original plant) and the long erect underground stems of sea
holly helped to give stability to the sand. A sea holly plant that
was dug up at Aberystwyth and sent to the Dulwich sand dune
by an 'old girl' had a vertical underground stem 35 in. long.
An enormous hole had to be dug to obtain the specimen unin-
jured. The viper's bugloss and sea holly formed beautiful
patches of colour against the leaves of sand sedge and sand
lyme grass.

SAND DUNES

101

PLANTS OF THE

Sand Sedge 1

Sand Lyme Grass I Chief

Marram Grass j Binders

Sea Couch Grass J

Sea Kale ]

Sea Holly I Other

Sea Bindweed f Binders

Sand Fescue Grass J

Prickly Saltwort

Frosted Orache

Sea Buckthorn

Sand Spurge

Sea Rocket

Sea Purslane

Rest Harrow

Viper's Bugloss

Biting Stonecrop

BirdVfoot Trefoil

Sand Stork's Bill

Sand Spurrey

Burnet Rose

Dog's-tooth Grass

Wormwood sp.

J.A.G.S. SAND DUNES

Carex arenaria
Elymus arenarius
Ammophila arenaria
Agropyron junceum
Crambe maritima
Eryngium maritimum
Convolvulus Soldanella
Festuca rubra var. arenaria
Salsola Kali
Atriplex laciniata
Hippophae rhamnoides
Euphorbia Par alias
Cakile maritima
Arenaria peploides
Ononis repens
Echium vulgare
Sedum acre
Lotus corniculatus
Erodium cicutarium
Spergularia rubra
Rosa spinosissima
Cynodon Dactylon
Artemisia Stelleriana

THE SALT MARSHES

A small salt marsh was made in 1905. Great difficulty was
experienced in obtaining the soil. Finally, a visit was paid to
a salt marsh near Gravesend, some soil was put into sacks, and
the sacks sent by train to Dulwich. When the sacks were
emptied in the botany gardens, the contents, slimy mud in
which were fragments of plants, looked most unpromising. But
the marsh proved a great success.

After making many experiments the girls concluded that the
best solution to be used in watering the plants was one contain-
ing 2 per cent, of salt. Tidman's sea salt was used at first, but
proved expensive, and common salt was substituted.

TRANSPIRATION IN SALT MARSH PLANTS

Many salt marsh plants are succulent, and show a reduction
in leaf surface, characteristics usually associated with plants
that live in dry habitats, such as members of the Cactaceae of
North American deserts, and the Sedums.

102 THE BOTANY GARDENS

For many years (1898-1911) it had been believed that these
salt marsh plants were unable to absorb water freely on account
of the saltness of the soil solution, and that this caused a low
rate of transpiration.

In 1911 Dr. E. M. Delf, an old girl', published the results of
her investigations on the transpiration of salt marsh plants, in-
cluding results of research work at the J.A.G.S. salt marsh. 1
She had already made observations on salt marsh plants at
Higham, and many visits were made to the artificial salt marsh
at the school, where observations were made on the stomates of
the sea aster (Aster tripoliuni) and annual marsh samphire (Salt-
cornia annua), which happened to be represented by particularly
flourishing plants, and on the sea blite (Suaeda maritima).

Dr. Delf found:

1 . That two typical salt marsh plants, annual marsh samphire
and sea blite, may have a high rate of transpiration per
unit of surface area, even greater than plants such as dog's
mercury and broad bean under similar conditions.

2. That these plants, when not already turgid, are able to
absorb water freely over their whole surface.

3. That the stomates in annual marsh samphire and in sea
aster are capable of opening and shutting, and are sensi-
tive to light and to variations in humidity, contrary to
statements by various previous workers.

Dr. Delf was early in the field to test by means of experiments
Schimper's theory of 'physiological drought'. She found it did
not hold in the case of salt marsh plants. The results of her
work were incorporated in articles contributed to Annals of
Botany. Dr. Delf was followed in the investigation of 'physio-
logical drought' by Montford who made experiments on bog
plants, and by Stocker who made experiments on heath plants
(see Chap. XI).

In 1913 another salt marsh was made as the original one was
small. It was arranged that soil from near Burnham-on-Crouch
should be sent, but unforeseen difficulties arose, and permission
from more than one authority had to be obtained before the
soil could be removed. The carriage of the soil by train was

1 'Transpiration and Behaviour of Stomata in Halophytes', Annals of Botany,
191 1 ; 'Transpiration in Succulent Plants', Annals of Botany, 1912. Thesis approved
for D.Sc. Lond.

SALT MARSHES 103

the chief expense. The sods when they arrived at Dulwich con-
tained marsh samphire, sea lavender, sea orache, and sea manna
grass. There was more than sufficient soil for the site chosen
near the pond, and another salt marsh was made in the new
piece of ground acquired by the Governors in 1912. Plants,
characteristic of salt marshes, have flourished in all three
marshes.

It did not seem likely, at first, that girls would take as much
interest in salt marsh plants as in the more beautiful plants in
the order beds, plots for pollination experiments, the wood and
the pond, but it has been evident in many years that great zeal
has been shown by those in charge of the salt marshes. The
girls who had charge of the salt marshes were only required to
water them with salt solution once a week, but they could often
be seen in the dinner-hour and after school making salt solution
and pouring it on the marshes. One year two girls poured
4,078 gallons on one salt marsh, using a two-gallon can and
having to go a little distance for the water.

Records of ten years show that the average amount of salt
solution given per year (chiefly in the summer term) was
730 gallons on one salt marsh, 480 gallons on another, and
1,107 on ^e largest salt marsh. Records also show that, in
eight years out of ten, girls in charge of salt marshes were
among those who had done the best work of the year.

Material from one of the salt marshes at J.A.G.S. is being
used in research work at the time of writing. There is in a salt
marsh made in 1913 a beautiful specimen of the shrubby sea
blite (Suaeda fruticosa) which has been there for more than
fifteen years. It forms a bush roughly 7 ft. in width and in 1933
the tallest branch was 4 ft. 7 in. high.

.Miss Martin, of Westfield College, is publishing a paper on
the two species of sea blite. She finds that the leaves from a
shrubby sea blite bush at the Chelsea Physic Garden, which
has had no salt, are less fleshy than those from a pebble beach
at Blakeney Point and Wells (Norfolk), and that leaves from
the J.A.G.S. plant, which has been watered at intervals with
a 2 per cent, salt solution, are intermediate in structure, being
on the whole less succulent than those from Blakeney.

In Miss Martin's paper presented at the British Association
meeting at Leicester 1933, there was an account of the anatomi-

104 THE BOTANY GARDENS

cal characters of the two species of sea blite, annual sea blite
(Suaeda maritima) usually growing in salt marshes, and shrubby
sea blite (Suaeda fruticosa) usually found on pebble beaches on
the edges of salt marshes, and an attempt to correlate their
outstanding features with the conditions of their environment.

PLANTS OF THE J.A.G.S. SALT MARSHES

Marsh Samphire Salicornia herbacea

Perennial Marsh Samphire Salicornia radicans

Annual Marsh Samphire Salicornia annua

Sea Plantain Plantago maritima

BuckVhorn Plantain Plantago coronopus

Sea Arrow Grass Triglochin maritimum

Sea Aster Aster Tripolium

Annual Sea Blite Suaeda maritima

Shrubby Sea Blite Suaeda fruticosa

Sea Manna Grass Glyceria maritima

Thrift Armeria vulgaris

Sea Heath Frankenia laevis

Sea Lavender Statice Limonium

Sea Mugwort Artemisia maritima

Sea Milkwort Glaux maritima

Sea Purslane Arenaria peploides

Sea Spurrey Spergularia marginata

Scurvy Grass Cochlearia danica

Sea Orache Atriplex portulacoides.

In one of the salt marshes the plants were arranged in
associations in the order they might be found, from the seaward
side of a salt marsh to the highest zone rarely covered by the
tide.

THE PEBBLE BEACH

A small pebble beach was made in 1909, but not of pebbles
from the sea-shore. The foundation was sea sand from
Lowestoft, and the girls brought pebbles of various sizes. Groups
of sea campion, sea pink, and other plants found on pebble
beaches were soon established. Although the plot was only a
small one, some interesting work was done in covering the sea
campion and sea pink plants with pebbles, and watching the
plants as they struggled through the stones.

In 1919 it was decided to make a pebble beach, or shingle
beach, next to the sand dune in the new playground, the sand
dune and pebble beach to merge into one another. The

1

s

I

<u

CJ

I

8

.Jn

PEBBLE BEACH 105

dimensions of the site were: length at back 24 ft., width 23 ft.
at the wide end, tapering off to nothing, the front being curved.

Construction. Soil was removed to a depth of 1 1 ft. ; 12 tons of
'coarse beach' material were sent from Brighton and spread
over the ground. The pebbles were piled up to a greater height
at the end adjoining the sand dune, and the 'beach' was
shallow at the end where it might be supposed the sea came up
to the beach. More material seemed needed, so another 6 tons
were obtained. It was very difficult without any previous
experience of the kind to gauge beforehand the amount that
would be needed.

Cost. The price of the first 12 tons was 8s. a ton, in truck loads
of 6 tons ancl upwards delivered carriage paid at East Dulwich
station. When the last 6 tons were ordered a letter was received
stating that owing to the bargemen having 'gone on strike'
their wages had been increased, and therefore the charge would
be IQS. 6d. per ton. In 1933 the price per ton delivered carriage
free at East Dulwich station was us. 6d.

In May 1920 yellow horned poppy, scurvy grass, sea pink,
and sea campion were put in the pebble beach. When a poppy
was planted some pebbles were removed, the root held in posi-
tion, and a little soil placed round the lower part of the long
root. Probably very little soil remained in position when the
pebbles were put round the upper part of the root. The poppy
plants flourished, and bore many flowers that summer and
following summers.

It was supposed that the roots had grown downwards until
they reached the soil, but when some of the pebbles were
removed, some months after the poppies had been planted, in
order to see what had happened, it was found that not one root
was in contact with the ground, and that none of the small
amount of soil that had been put with the roots was to be seen.

The yellow horned poppies that had been left in the shingle
produced seeds and many young plants developed. These
young plants showed their preference for easier conditions than
prevail on a pebble beach by forming a line along the junction
of pebbles and path, some distance from the parent plants.
Some seedlings, however, developed among the pebbles.

Imitation of Natural Conditions, (i) From time to time some of
the plants, sea campion, sea pink, and yellow horned poppy,

4158 P

io6 THE BOTANY GARDENS

were subjected to the proper 'overhead treatment' character-
istic of mobile shingle. They were covered, or nearly covered,
with pebbles. The plants grew through the stones, and seemed
more vigorous after the treatment. (2) After the pebble beach
had been in existence seven or eight years some seaweed was
put on the shingle every year, imitating the 'drift* that occurs
in Nature. On natural sea beaches detached seaweed and other
organic debris arc thrown up by the waves on the beach, and
these form an important source of 'humus' for the shingle-
beach plants.

PLANTS OF THE J.A.G.S. PEBBLE BEACH

Poppy, Yellow Horned Glaucium luteum

Scurvy Grass Cochlearia officinalis

Shrubby Sea Elite Suaeda fruticosa

Sea Beet Beta maritima

Sea Campion Silene maritima

Sea Kale Crambe maritima

Sea Lavender Statice Limonium

Sea Mertensia Mertemia maritima

Sea Pea Lathyrus maritimus

Sea Pink Armeria vulgaris

Sea Purslane Arenaria peploides

Stonecrop, Biting Sedum acre

XIII

THE CORNFIELD. THE MEADOW. CHALK BEDS.

THE WALL. MENDELIAN EXPERIMENTS. SOIL

EXPERIMENTS

THE CORNFIELD

A SMALL cornfield was made in 1902. It was useful, the
girls were interested in it, and some paid visits to cornfields
to obtain seeds of various 'weeds' of the cornfield: poppy, corn-
flower, corn-cockle, corn marigold. But the ground was wanted,
and the cornfield ceased to exist.

For some years other developments more important were
needed, but early in 1926 a plot of ground, 66 ft. by 10 ft., was
given for a cornfield. The turf was removed, and the ground
dug. In 1928 another piece of the same size, adjacent to the
first, was added and a path was left between the two pieces.

Sowing of corn. For the first two years Yeoman King Wheat
was sown in rows. In the third year the following were sown:

Wheat Red Stand Up

Oats Giant Black Winter

Barley Six-rowed Winter

Rye Giant Star

Wheat, oats, barley, and rye were sown in other years. With
the exception of one year, this was done in the autumn term.

The crop grew well but often the harvest was spoilt by birds.
In some years netting was used and proved fairly successful in
protecting it.

. The crop is cut each year in the late summer and the ground
dug over. A dressing of superphosphate, kainit, and ammonium
sulphate was given to the field one year.

Weeds of the cornfield. The weeds of a cornfield are mostly
annuals, often introduced with impure seed. Perennials do not
thrive when the soil is disturbed every year.

Dr. Brenchley, the chief botanist at the Rothamsted Experi-
mental Station, and an 'old girP, in Weeds of Farm Lands states:
'The cereals form a group of plants that collectively has less

io8 THE BOTANY GARDENS

direct influence upon the weed flora than any of the other types
of crops', and 'Every weed of any importance is found among
all the cereals, but some are more particularly encouraged or
discouraged by one or other of them'.

Typical cornfield weeds would doubtless have appeared of
themselves in the cornfield made at J.A.G.S., but it might
have been some time before there was a representative collection,
so seeds were sown. In time the weeds thrived and began to be
self-sown.

The cornfield now proves a great attraction with its rows of
wheat, barley, oats, and rye, and among the corn the gay
flowers of red poppies, scarlet pimpernels, corn-cockles, and
heartsease.

PLANTS OF THE J.A.G.S. CORNFIELDS

Red Poppy Papaver Rhoeas

Corn-cockle Lychnis Githago

Scarlet Pimpernel Anagallis arvensis

Corn Buttercup Ranunculus arvensis

Heartsease Viola tricolor

Spurrey Spergula arvensis

Sun Spurge Euphorbia Helioscopia

Corn Marigold Chrysanthemum segetum

Cut-leaved Crane's-bill Geranium dissectum

Field Madder Sherardia arvensis

Shepherd's Needle Scandix Pecten-Veneris

Silene quinquevulnera

THE MEADOW

The meadow was made in two adjacent pieces of land, 50 ft.
by 25 ft. and 65 ft. by 1 8 ft. They were dug over and a path was
left between them. The following grasses were sown in 1926:
crested dog's-tail, cock's-foot, meadow foxtail, Timothy, peren-
nial rye grass, Italian rye grass, smooth meadow grass. Some
typical meadow plants other than grasses were planted. The
hay is cut every year.

Plants of the meadow. As a rule in a meadow the plants are
chiefly grasses and leguminous plants, with a variety of species
belonging to other families. They are nearly all perennials.

In the J.A.G.S. meadow the cock's-foot grass grew so strongly
that it overpowered the finer grasses and other plants, and some
clumps were removed.

THE MEADOW 109

Typical meadow plants and seeds of meadow plants, other
than grasses, were planted in various years after the first year.
Such plants have been classified as follows: 1

A. Plants that must be regarded as weeds in all circum-
stances, (i) poisonous plants, (2) coarse growing plants
that deteriorate the quality of the meadow, (3) plants of
low feeding value, (4) parasitic weeds.

B. Plants that are considered to possess a certain feeding
value, but are regarded as weeds if they are present in too
great quantity.

C. Plants which are difficult to class definitely as weeds, but
are noxious if present in too great abundance. Probably
most are of some use as food.

GRASSES OF THE J.A.G.S. MEADOW

Crested Dog's-tail grass Cynosurus crislatus

Cock's-foot grass Dactylis glornerata

Meadow Foxtail grass Alopecums pratemis

Timothy grass Phleum pratense

Perennial Rye grass Lolium perenne

Italian Rye grass Lolium italicum

Smooth Meadow grass Poa pratensis

OTHER PLANTS OF THE J.A.G.S. MEADOW

Red Clover Trifolium pratense

White Clover Trifolium repens

Alsike Clover Trifolium hybridum

Dog Daisy Chrysanthemum Leucanthemum

Meadow Buttercup Ranunculus acris

Bulbous Buttercup Ranunculus bulbosus

Sorrel Rumex acetosa

Meadow Saxifrage Saxifraga granulala

Burnet Saxifrage Pimpinella saxifraga

Common Vetch Vicia saliva

Lady's Smock Cardamine pratensis

Wild Angelica Angelica sylvestris

Sneezewort Achillea Ptarmica

Yarrow Achillea Millefolium

Lesser Stitchwort Stellaria graminea

Chervil Anthriscus sylvestris

Wild Carrot Daucus Carota

Fleabane Pulicaria dysenterica

Pignut Conopodium denundatum

Salad Burnet Poterium Sanguisorba

1 Weeds of Farm Land, Brenchley, 1920.

THE BOTANY GARDENS

OTHER PLANTS OF THE J.A.G.S. MEADOW (continued)

Cat's Ear Hypochaeris radicata

Cowslip Primula verts

Mouse-ear Hawkweed Hieracium pilosella

Ragged Robin Lychnis Flos-cuculi

Hawkbit Leontodon hispidus

Field Scabious Scabiosa arvensis

Marsh Thistle Cirsium palustre

Meadow Pea Lathyrus pratensis

Knapweed Centaur ea nigra

Smooth Hawk's-beard Crepis virens

Lady's Bedstraw Galium verum

Great Burnet . Sanguisorba qfflcinalis

Musk Mallow Malva moschata

Thyme-leaved Speedwell Veronica serpyllifolia

Early Purple Orchid Orchis mascula

Spotted Orchid Orchis maculata

*Yellow Rattle Rhinanthus Crisla-galli

*Red Rattle Pedicularis palustris

*Eyebright Euphrasia qfficinalis

*Viscid Bartsia Bartsia viscosa
* Not established.

CHALK BEDS

In 1904 two small pieces of ground, each 12 ft. by 4 ft.,
were set aside for plants which usually grow on chalk and
limestone soils. The top part of the garden soil was removed,
and chalk soil from a district in Surrey was put in the beds. In
1928 four cubic yards of chalk soil were sent as a present from
another part of Surrey, where excavations for road making
were in progress, and another bed for chalk plants was made in
the newer part of the botany gardens, after the garden soil had
been dug out to a depth of 1 8 in.

PLANTS OF THE J.A.G.S. CHALK BEDS

Baneberry Actaea spicata

Beech Fagus sylvatica

Bladder Campion Silene Cucubalus

Box Buxus sempervirens

Burnet Saxifrage Pimpinella saxifraga

Columbine Aquilegia vulgaris

Crested Hair-grass Koeleria cristata

Cut-leaved Germander Teucrium Botrys

Dropwort Spiraea Filipendula

CHALK BEDS

in

PLANTS OF THE J.A.G.S.

Dwarf Thistle

Eyebright

Field Flea-wort

Foetid Iris

Glaucous Sedge

Great Mullein

Ground Pine

Hare's Ear

Hoary Plantain

Juniper

Lady's Bedstraw

Lady's Fingers

Milkwort

Mouse-ear Chickweed

Mouse-ear Hawkwecd

Nettle-leaved Campanula

Orchids: Bee

Fly

Man

Spider

Spotted
Pasque Flower
Privet

Purging Flax
Rest Harrow
Rock Rose

Round-headed Rampion
Sainfoin
Salad Burnet
Silver-weed
Small Scabious
Stinking Hellebore
Thyme
Tufted Vetch
Tway-blade
Upright brome grass
White Helleboririe
Whitlow Grass
Wild Mignonette
Yellow-wort

CHALK BEDS (continued)

Cirsium acaule

Euphrasia qfficinalis

Senecio integrifolius (campestris)

Iris foetidissima

Carex glauca

Verbascum Thapsus

Ajuga Chamaepitys

Bupleurum rotundifolium

Plantago media

Juniperus communis

Galium verum

Anthyllis Vulnerana

Polygala vulgaris

Cerastium arvense

Hieracium pilosella

Campanula Trachelium

Ophrys apifera

Ophrys muscifera

Aceras anthropophora

Ophrys aranifera

Orchis maculata

Anemone Pulsatilla

Ligustrum vulgare

Linum catharticum

Ononis spinosa

Helianthemum vulgare

Phyteuma orbiculare

Onobrychis viciaefolia

Poterium Sanguisorba

Potentilla anserina

Scabiosa columbaria

Helleborus foetidus

Thymus Serpyllum

Vicia Cracca

Listera ovata

Bromus erectus

Cephalanthera grandifiora

Draba muralis

Reseda lutea

Chlora perfoliata

THE WALL

A short wall was built of large pieces of stone with soil in
between them. Wall plants and their seeds were put in the soil.
Some were difficult to establish and the wall did not compare

ii2 THE BOTANY GARDENS

favourably with some old walls to which presumably the seed
had been carried by wind or other agents.

After the wall in the botany gardens had been in existence
several years it was pulled down and the plants and soil were
put between the layers of stone as the wall was built. It was
found that the plants were anchored more firmly.

PLANTS ON THE J.A.G.S. WALL

Biting Stonecrop Sedum acre

Black Spleenwort Asplenium Adiantum-nigrum

Ivy-leaved Toadflax Linaria Cymbalaria

Lanceolate Spleenwort Asplenium lanceolatum

Maidenhair Spleenwort Asplenium Trichomanes

Pellitory-of-the-Wall Parietaria officinalis

Red Valerian Centranthus ruber

Shining Crane's-bill Geranium lucidum

Scaly Fern Ceterach qfficinarum

Snapdragon Antirrhinum majus

Wallflower Cheiranthus Cheiri

Wall Pennywort Cotyledon Umbilicus

Wall-Rue Spleenwort Asplenium Ruta-muraria

VARIATION

1 . As an introduction to the study of variation, collections
were made of leaves from one individual plant. Leaves from
a mulberry-tree showed considerable variation in their shape.
They were pressed and mounted, and kept for reference.

2. The lengths of 100 haricot bean seeds were measured.
The results were then shown in a graph, and the actual bean
seeds were mounted in vertical rows on black cardboard, thus
illustrating the variation pictorially.

3. The ray florets of hundreds of common daisies were
counted. One year the number varied from 20 to 57 in a head,
and by plotting a curve the variation was graphically repre-
sented. The experiment was repeated each year for years, and
the results combined, a new curve with a more smooth outline
being obtained with apparently two modes.

4. Graphs showing variation in the number of rays in umbels
of hedge parsley were also made.

STRUGGLE FOR EXISTENCE

i. One hundred and seventy-five acorns were planted in
November 1922 outside the wood, in a small plot 23 ft. 10 in.

STRUGGLE FOR EXISTENCE 113

by 6 ft. 4 in. A great number germinated. At Professor
Tansley's suggestion they were left 'to fight it out', and show
the survival of the fittest.

In 1922 178 acorns planted.
1926 133 oak trees.

1929 J 25
1931 122
1932 98

2. A map has been made of the vegetation in a plot 15 ft.
square in the wood, and a study is being made of the struggle
for existence between dog's mercury and bluebells.

MENDELIAN EXPERIMENTS

All the experiments at J.A.G.S. to investigate Mendel's Laws
of Inheritance were made by girls of post-matriculation stage.

i. ist year. Crosses were made between pea plants grown
from seeds having yellow cotyledons and plants grown from
seeds having green cotyledons.

Seeds were obtained as a result of the crossing which on
examination were all found to have yellow cotyledons. 1 Thus
yellowness was a dominant character. These seeds were kept to
continue the experiments the following year.

2nd year. The seeds were sown and the resulting plants
all yielded seeds, some of which had yellow and some green
cotyledons.

The numerical results were as follows:

637 seeds with yellow cotyledons, 215 with green, or a ratio of
3 : i -01 . According to Mendelian laws the ratio should be 3 : i .
The experimental result thus shows a very close approximation
to the theoretical. Expressed in a table:

Yellow cotyledons X Green cotyledons

I

F l Generation. Yellow cotyledons

1

F 2 Generation. Yellow Yellow Yellow Green
1 It is necessary to chip each seed to ascertain the colour of the cotyledons.

4158

114 THE BOTANY GARDENS

2. Further experiments were made with pea seeds kindly sent
from the John Innes Horticultural Institution. The sincere
thanks of the J.A.G.S. Botany Department are also due to this
institution for help and advice as to methods of procedure.

istyear. Crosses were made between pea plants differing
in the following characters:

SET A SET B

Acacia leaves (no tendrils). Normal leaves with tendrils.

Normal stems. Fasciated stems.

Emerald (non-glaucous), chiefly stipules Glaucous.

and pods.

White flowers. Purple flowers.

Green pods. Purple pods.

Method of procedure. Fingers and forceps, which had been
sterilized in alcohol, were used for turning back the wings and
keel of a bud of a plant in Set A, and for plucking out the
stamens. Care had to be taken that the stamens were still
unripe.

After the removal of the stamens the wings and keel were
released and again enclosed the pistil. A small square of
muslin was then folded in half over the bud and pinned, and
a small label bearing the plant's number was attached to the
stalk of the bud.

(Every plant was given a registration number, such as | g or
5 5 j, the denominator indicating the year.)

After twenty-four hours the muslin was removed, the wings
and keel were again turned back, and the exposed style was
pushed into the inverted keel of a flower which had just been
picked from a plant of Set B. During the operation of turning
back the wings and keel, this flower was held by its stalk in the
mouth of the experimenter in order to set both hands free.
Holding the flower in an inverted position during the process of
pollinating facilitated the entrance of the style of the bud into
the keel of the flower. The pollinated bud was then re-pinned
in muslin and the number of the plant supplying the pollen
added to the label. The muslin was removed when the pod
began to form.

The seeds obtained as a result of these crosses were harvested.

MENDELIAN EXPERIMENTS 115

2nd year. The above seeds were sown and all yielded F x
(first filial generation) plants showing the dominant characters
of the pairs of characters under consideration.

Fj Generation.

Normal leaves
Normal stems
Glaucous
Purple flowers
Purple pods

3rd year. The seeds of the F! plants were sown and the F 2
plants examined for the characters set out above.

F 2 Generation.

Scliool result

Theoretical result

Normal leaves v. Acacia
Normal stems v. Fasciated
Glaucous v. Emerald
Purple flowers v. White
Purple pods v. Green

96 : 29
89 : 36

94:3i
92 : 30

67:57

93:31
93:31
93:31
9i-5 : 30-5
72 : 56

3 : *
3 : i
3: i
3 : i
9: 7

3. Red snapdragons were crossed with white, and the flowers
of the plants of the resulting F t generation were all an inter-
mediate shade. Parents and offspring plants were on view
in plots.

The F 2 generation yielded a variety of colour forms: 5 different
red types could be distinguished and 2 white or yellow. Of
63 plants examined the ratio of those showing red colour to
those without it was 46 : 17. (The 3 : i ratio is approximately
47 : 16.)

SOIL EXPERIMENTS

' Some bacteria of the soil which enter the root-hairs of many
of the plants of the family Leguminosae and other plants are
able to use the free nitrogen of the air and make nitrogen com-
pounds. They form swellings on the roots, the root tubercles.
Some of the bacterial cells of the tubercles are digested by the
plant, which thus obtains an extra supply of nitrogen.

Lupin plants were grown in a plot at J.A.G.S. from 1901
to 1909 and good specimens were obtained of tubercles on
roots, A crop of lupin plants improves poor soils. It increases

n6 THE BOTANY GARDENS

the supply of available nitrogen. In 1906 experiments were
made on two adjacent plots of sweet pea plants. One was
watered with ordinary water, and one with a bacterial culture
solution, the material for which was kindly supplied by King's
College, London. Not much difference was seen in the develop-
ment of the plants, and Professor Bottomley thought that plants
growing in poorer soil would have shown a greater difference.
In the farming of poor soils inoculation with the bacteria
which form root tubercles has been found advantageous.

Effect of absence of manure. Wheat was grown in the same
two plots from 1901 to 1909, year after year, without any
manure being given. The same number of grains were sown
each year, and the crops watched and gathered. It was in-
tended that this experiment should go on for many years like
the famous experiment at Rothamsted, but the ground was
needed for the making of a lane in 1909, and the experiment
was stopped. The later crops of wheat were certainly not so
good as the early ones.

MANURIAL EXPERIMENTS

1. Water-cultures. The growth of plants in normal food
solutions and in solutions lacking one of the following elements:
phosphorus, nitrogen, magnesium, calcium, sulphur, iron, or
potassium, may be said to be of the nature of manurial experi-
ments. (See Chap. III.)

2. Influence of nitrates on leaf development. Small Brussels
sprout plants were grown from seed in large pots. One pot
contained ordinary garden soil, the other, soil supplied with
extra nitrate. There was much greater leaf development in the
plants supplied with extra nitrate.

3. Field experiments. Effects of artificial manures. The

soil in a piece of ground approximately 23 ft. by 18 ft. was dug
over and limed, and the ground divided into five plots. Mustard
seed was sown thinly in rows 9 in. apart, three rows in each
plot. The plants were thinned at intervals until they were
from 4 to 6 in. apart. In the first year of the experiment, when
the plants were well above the ground, chemical manures were

MANURIAL EXPERIMENTS 117

spread over the surface of the ground between the rows in four
of the plots, but in succeeding years the manures were applied
to the soil before the crop was sown. The following chemical
manures were used:

Plot i . No manure.

Plot 2. Complete manure.

5 oz. superphosphate.

2j oz. sulphate of ammonia.

3 oz. sulphate of potash.

Plot 3. Manure lacking potash.
5 oz. superphosphate.
2j oz. sulphate of ammonia.

Plot 4. Manure lacking phosphate.

2 J oz. sulphate of ammonia.

3 oz. sulphate of potash.

Plot '5. Manure lacking nitrogen.
5 oz. superphosphate.
3 oz. sulphate of potash.

Sulphate of potash was used instead of kainit as it is a suitable
manure for spring application, and kainit should be applied in
the winter. Superphosphate was used instead of basic slag as it
is more suitable for use in the spring.

Appearance in the field. The plants in soil supplied with
complete manure were more vigorous than the plants in other
plots, especially than those in the plot with no manure. The plants
supplied with manure lacking nitrogen were poorer than those
in the plots supplied with manure lacking phosphate or potash.

The crops of all five plots were harvested when the plants
were in full flower, and the first fruits were developed but not
ripened. The plants were cut off at ground-level. The green
weight was taken in the field, compression balances being used.
The crop from each plot was air-dried separately. There are no
facilities for drying at 100 C. all the material from each plot,
so two duplicate air-dried samples taken from each set were
weighed, dried in a water-oven, and an average factor obtained.

If x constant air-dried weight of sample, and

y = constant oven-dried weight of sample,
v/x multiplied by the constant total weight of air-dried
material from a plot gives the amount of dry matter in the plot.

1 18 THE BOTANY GARDENS

The percentage of dry weight in the green weight can then be
found. The results obtained from the plants of the five plots
are summarized in tabular form.

Plot

Treat-

ment

Green

wt.
of crop

Const, air-
dried wt.
of crop

Wt.of
sample

Const,
oven-dried

wt. = y

Fraction

Percentage
dry wt.

Fresh crops have been sown, and the experiments are still
being carried on. It is hoped that a number of results will be
recorded from which conclusions may be drawn.

Thanks are due to Dr. Brenchley of the Rothamsted Experi-
mental Station for the help and advice given when the experi-
ments were begun and during their progress.

XIV
THE WOODS

A SMALL wood was made in 1909. No school money was
available. Some of the trees were given by girls when they
left school to commemorate their school life, especially their
connexion with the botany gardens. Mistress and girls obtained
plants for the ground vegetation. The wood was of great use in
those early days, but it was too small, and did not represent any
type of English wood.

When the Governors acquired a large field, a piece of ground,
about a quarter of an acre in extent, was set aside for the new
wood. The plot was in the shape of an irregular four-sided figure.
The ends measured 102 ft. and 45 ft., the sides 153 ft. and 164 ft.

The ground was trenched three spits deep in 1914, care being
taken that the soil was replaced at its original level, the subsoil
not being brought to the surface.

Type of wood. The fact that the soil at Dulwich is clay, and
also that the ground vegetation of a 'damp oakwood' is a most
attractive one, led to the decision that the wood should be of
the type known as a damp oakwood, having Quercus robur
(Qj pedunculatd) as the dominant tree. It was decided that a
small part of the wood should be planted with ash trees, and
that a deep hollow should be made for damp-loving herbaceous
plants, and the hollow surrounded by willows.

A border 6 ft. wide was to be left on three sides of the wood,
and typical woodland shrubs and small trees planted in it.

'Oak Trees. Reference to many authorities was made before
the size of the trees to be planted was settled. Some advised
oaks 2 to 2 1 ft. high, others 3 to 5 ft., 4 to 6 ft., and even second-
year seedlings. Finally 2 to 3 ft. was the height chosen.

Hard woods, such as oak and ash, are usually planted some
distance apart, and the spaces between the trees filled in with
Scotch fir, or spruce, or larch, to act as 'nurses' to be removed
as the oak and ash trees grow. It was felt that the 'nurses' might
live and not the oaks, so it was decided that the oak trees were

120 THE BOTANY GARDENS

to be placed very close to each other, only 3 ft. apart, in order to
obtain a canopy as soon as possible, and to enable the leaders
to run up 'straight and clean', and as the trees grew some of the
least promising were to be removed.

Estimates were obtained from six well-known forest tree
growers, and then by request samples were sent by two of the
firms and the choice was made.

Ash trees* Ash trees were planted in the wood in order that
the ground vegetation under them could be compared with that
under the oak trees, as the plants became established. The trees
when planted were 5 to 6 ft. in height.

Willows. The firm that supplied the oak trees sent willow
cuttings to ensure an equal number of staminate and pistillate
trees, but these were so unsightly that only a few were used,
and these did not live. In 1915 twenty-five young goat-willow
trees, 4 to 5 ft. high, were planted. Unfortunately, as was
seen later, there were many more pistillate than staminate.
The willows have been so popular with the bees that in the
spring a loud humming noise has often been heard on entering
the wood.

Planting of oak and ash trees. It was considered
advisable that the firm that supplied the trees should send a
planter. He came on December 2ist, 1914, and in little more
than two short days (the sun set before 4 o'clock) he planted
783 oaks and 61 ash trees, 3 ft. apart in all directions. All the
trees lived.

The cost of the 844 trees plus the planting was 8 i6s. 6d. 1

The border. In the spring of 1915, 200 bramble plants were
put in the border on three sides of the wood. In the autumn
many shrubs and small trees were added: hazel, hawthorn,
sloe, spindle, crab-apple, gean, maple, honeysuckle, wild rose,
and others. The cost of 244 shrubs and small trees for the
border was 2 1 6s.

1 Prices of trees, autumn 1933:

Oaks . . . . 2 to 3 ft., 17-y. 6d. and 2U. per 100.

Ash 3 to 4ft., 1 5*. per 100.

Bramble plants . . 155. per 100.

THE WOODS 121

The ground flora. Primroses, bluebells, wood anemones,
and campions were put in the wood in 1915 soon after the oak
and ash trees were planted. Every year more plants were added
to the ground flora, and many of those already in the wood
gave rise to others, some by seeds, some by vegetative reproduc-
tion. In 1919 there were thousands of bluebell plants, 550
primrose plants, 500 dog's mercury, 350 lesser celandine, 300
wood anemones, as well as yellow dead-nettles, early purple
orchids, tway-blades, and other plants. At the time of writing
there are many more in some cases, thousands of these
plants, also those of other genera and species.

We were fortunate in hearing through one of H.M. Inspectors
that a road was being cut through a wood on the outskirts of
London, and that great numbers of bluebell bulbs were being
dug up and thrown away.

Girls from several forms made expeditions to the wood in
their holidays, and nearly 3,000 bluebell bulbs were brought
back and put in the J.A.G.S. wood.

The wood is beautiful in the spring with the unfolding leaves,
a deep blue haze of bluebells, and hundreds of primroses and
campions in the carpet of dog's mercury plants.

COMPETITION OF WOODLAND PLANTS AND WEEDS

Before the oak and ash trees grew and afforded shade the
ground vegetation had a great struggle with grass and other
plants, and many 'aliens' had to be removed. The most
rampant weeds in the wood soon after the trees were planted
were grass, clover, groundsel, coltsfoot, and creeping buttercup.
In 1916 they had increased so much that girls volunteered to
come in the holidays and remove them, and some clearance of
weeds was effected.

The excessive growth of meadow grass among the ground
flora was overcome by time. When the trees had grown suffi-
ciently to afford a close canopy the grass did not survive. A
year after the trees were planted thousands of groundsel plants
flourished, but were exterminated in 1 9 1 6. Coltsfoot was difficult
to eradicate. The flower heads were cut off as soon as they
appeared to prevent fruit being formed. In March 1918,
3,105 coltsfoot plants were dug up, and the wood was soon free
from them.

4158 R

122 THE BOTANY GARDENS

Creeping buttercup was by far the worst 'alien', and at one time
it seemed as if it would be the conqueror. When the ground was
trenched, and when the oaks were planted, not one buttercup
plant was seen. In 1917, 7,865 plants were removed in May
and July, but in 1918 the number had increased so enormously
that a special effort had to be made so that the girls should not
have to acknowledge themselves beaten by the plants. A
'buttercup week' was instituted, and girls throughout the school
left work in their own gardens to help in the wood: 33,380
buttercup plants were removed in the week. The plants had
multiplied by runners and by seed, but chiefly by runners.
One plant was dug up with 30 young plants attached to it. In
1919, early in the year, 239,268 plants were removed, and the
next year 162,227. The year 1920 saw the conquest of the
buttercup. After 1923 it was difficult to obtain any plants
wanted for class specimens. Nearly half a million plants had
been removed by the girls in four years.

AGE AT WHICH ACORNS ARE BORNE

When it was decided in 1914 that the wood should be of the
damp oakwood type it was expected that it would be many
years before any fruit would be formed. Marshall Ward gave
20 to 30, or even 80 years, before oaks would bear flowers.
Another authority stated: 'The tree does not commence to bear
good fruit until the ripe age of 60 or 80 years.'

In September 1918 eleven acorns were found, some on the
ground, some on trees. On reference to the growers the age
of the trees when planted in December 1914 was ascertained
to have been from 3 to 4 years. The age at which fruit was
borne on some trees was, therefore, 7 to 8 years. As this seemed
abnormal a letter was sent to the Director of Kew Gardens
stating the facts.

The Director, in reply, stated it was unusual for Quercus
pedunculata to produce acorns when only seven or eight years
old, but that Mr. Elwes in Trees of Great Britain and Ireland, says
it 'begins to bear at a very early age in some cases'. In 1906
Mr. Elwes received a packet of acorns taken from trees ten
years old. According to Dr. Hemsley in Hooker's Icones Plan-
tarum several authors have mentioned the common oak as
occasionally flowering in the seed beds. 'Trees do not produce

THE WOODS 123

full masts until they are about 70 years old' (Schlich, Manual
of Forestry] .

Acorns were found at Dulwich in other years:

15 in 1919 1,221 in 1924 4,618 in 1929

o in 1920 510 in 1925 6 in 1930

43 in 1921 10 in 1926 466 in 1931

3,105 in 1922 132 in 1927

o in 1923 213 in 1928

Marshall Ward pointed out that it was quite usual for a year
with a heavy crop of fertile flowers to be followed by two or
three years without flowers.

Seventeen years after the trees had been planted 10,350
acorns had been found. In most of these years there were
probably more acorns formed than recorded, as when the girls
returned in September there were many leaves on the ground,
and acorns under and between leaves are not easily seen.

It was thought by some experts that the early age at which
acorns were borne at J.A.G.S. was a bad sign for the future
condition of the oak trees, but, in 1924, the tree expert from
whom the trees had been bought visited the wood, pronounced
it to be in good condition, and pointed out a number of very
promising trees.

Germination of acorns. Some of the acorns produced in 1 9 1 8
were sown in pots in February 1919 and did not germinate, but
the non-germination might have been due to the acorns having
been kept too long before they were planted, since it is known
that acorns, if kept dry, soon lose the power of germination.
Acorns of the 1919 crop were planted in December of the same
year, and some did germinate. In the spring of 1921 a young
oak seedling was found in the wood. In 1922, 175 acorns were
planted and 133 germinated.

Lammas shoots. When trying to decide the age of the trees
when fruit was first formed we were warned not to rely on bud
scale scars, as the formation of Lammas shoots is quite frequent
in Quercus. This led to an attempt being made to demonstrate
the formation of these shoots. In the early part of 1919 pieces
of red string were tied just below the terminal buds of branches

124 THE BOTANY GARDENS

on forty oak trees, but in the late autumn it was found that no
Lammas shoots had been formed on those branches. When this
was repeated in 1922, however, Lammas shoots were found.

BIRDS' NESTS

While the trees were very small no nests were seen, but when
they had been planted a little more than five years a blackbird
was seen on a nest in a willow tree near the dell.

Next year (1921) a hedge-sparrow built a nest low down in
a bramble bush and four eggs appeared. Another hedge-
sparrow built in the bramble, and two blackbirds in the haw-
thorns. The eggs in all four nests were hatched and the young
birds flew away. A blackbird in the same year built in an oak
tree.

1923 was a good year for nests. Three blackbirds nested in
hawthorn bushes, four hedge-sparrows in brambles, and a thrush
high up in an oak tree and three young thrushes were seen in
the nest. (A blackbird also nested in the lane.)

It is now quite a usual thing for birds to build in the wood.
Intense interest is shown by the girls, indeed at times the interest
is almost too great, but the nests are not examined until they
are deserted.

The wood affords a good opportunity for the study of bird
life: identification of the bird inhabitants by their calls, their
songs, and their appearance.

THINNING OF THE WOOD

The oak trees planted at the end of 1914 grew well, and in
1919 had made such thick growth that advice as regards
thinning was sought from the grower. He replied: 'You must
be careful not to thin oaks too soon. It is most important that
the boughs should shade the ground; also you require tall, clean
stems, which are only procured by close growth. . . . To sum up:
You may gradually thin, but it is most important to maintain
canopy always.'

A tree expert in charge of some parks came to see the wood.
He also emphasized the necessity of a canopy and straight
leaders, and did not advise thinning. He was so interested in
the wood that he would accept no fee !

In 1922 the head of the firm who had supplied the trees visited

THE WOODS 125

the wood. He advised that 1 50-200 oak trees should be removed,
including all those that had lost their leaders. In the summer
and autumn 200 oak trees were removed and 2 ash trees.

In 1924, 35 oak trees were taken out, the lowest branches of
all oaks 'thinned off', and several willows removed. More light
was admitted into the wood by cutting back the hawthorns,
hazels, and maples of the shrub border.

In 1926 advice was given that all rival leaders in the oaks
should be pruned, that ash trees badly attacked by scale insect
should be taken out, and others affected by it should be scrubbed
with strong soft-soap solution. In this year 52 oaks, i willow,
and 7 ash trees were removed. In 1931 there was a good report
on the condition of the oak and ash trees the willows were
dying out owing to oak and ash trees growing up round them
and cutting off the light supply. Fifty-six oak trees were cut
down.

NUMBER OF TREES IN THE WOOD

1914 December 1931 September

783 Oaks 298 Oaks

6 1 Ash 53 Ash

25 Willows 13 Willows

PLANT DISEASES IN TREES OF J.A.G.S, WOOD

1. The oaks in 1924 were attacked by a fungus which formed
white spots on the leaves and caused them to shrivel and turn
brown. The fungus was identified at the British Museum
(Natural History Department) as Oidium alphitoides, an oak
mildew. It first appeared in Europe about 1906 or 1907, and
rapidly spread.

2. The ash trees were attacked by a scale insect, the 'ash
coccus'.

CHANGING CONDITIONS IN THE WOOD

The gradual change in the condition of the wood and its
increase in distinctively woodland conditions have been most
interesting to study and record.

As the young trees grew and developed more leaves, experi-
ments were made to investigate the gradual changes in the
conditions to which the ground vegetation was subjected. The
experiments dealt with:

i. The soil. The humus content.

126 THE BOTANY GARDENS

2. The atmosphere.

(a) The temperature of the air inside the wood compared
with that outside.

(b) The total evaporating power of the air.

3. The light intensity to which the ground vegetation was
subjected.

i. Humus content of soil.

The soil of the field where the new wood was made was poor
in humus, and for some years when the trees were very young not
many leaves enriched it. When the wood had been made eight
years the percentage of humus in the soil from a part outside
the dell was only 7-94, in 1929 it was 9*1, and in 1931, 10-2.

But the soil in the dell (the hollow surrounded by willows) is
richer in humus than other parts. The trees are closer, the
leaves on the ground are rarely disturbed, and the percentage
of humus increased more rapidly. In 1925 it was 15*9, in
1929, 18-2, and in 1931, 20.

Twenty-six experiments have been made in various years to
find the humus content of the soil outside the dell and seventeen
to find that of the soil inside the clell. In every year in which
records have been kept but one, the percentage of humus was
practically twice as great in the soil inside the dell as in that
outside.

The percentage of humus in some soil brought from a wood
in Kent was found to be 24-25 the average result of ten
experiments.

2. The atmosphere.

(a) Comparison of temperature inside and outside the
wood. Maximum and minimum thermometers were placed
inside the old wood and the new wood and outside each wood in
the open, in the year 1917-18. The readings were taken about
the same time, 1 1 a.m. in the mid-morning recess.

New wood. Two hundred and eighty-one readings were taken
of the maximum and minimum temperatures of the air inside
the wood and outside it during a period of five years. On more
than half the number of days the maximum temperature inside
the wood was less than that outside. When the readings were

THE WOODS 127

first taken the trees were very young. In the first year of
temperature records the maximum temperature inside was less
than that outside on 47 days only out of 152 (30*9 per cent.),
and the minimum temperature of the air inside the wood more
than that outside on only 46 days (30-3 per cent.).

In 1920 when the trees had developed more leaves the maxi-
mum temperature inside was less than that outside on every
day the observations were made, and the minimum temperature
more than that outside on 78-6 per cent, of the days.

Old wood. In a total of 138 observations made during a
period of three years the maximum temperature in the wood
was lower than that outside on 1 19 days (86-2 per cent.) and the
minimum temperature was higher on 93 days (67-4 per cent.).

It should be recorded that the trees of this wood are older
and have a denser canopy than those of the new wood, also
that in the old wood, 122 of the 138 observations were made
after May ist when the leaves had opened. In the new wood
the observations were made throughout the year.

(b) Comparison of total evaporating power of atmosphere
inside and outside the wood. For these experiments Living-
ston's porous cup atmometers are used, the non-absorbent form
in order to avoid errors due to rainfall. 1 There was great
difficulty in obtaining a supply of porous cups from America
during the War, and it was not until July 1919 that one atmo-
meter was placed in the middle of the wood and one outside.
Two sets of observations are made. The girls in Form VI who
are specializing in science usually make these experiments.
The total number of comparisons between the evaporating
power of the air inside the wood and the air outside in eleven
yars has been 92. In every case the quantity of water evapor-
ated from the atmometer outside the wood has been greater than
the quantity evaporated from the one inside in the same period.

The observations are usually made in the summer term. In
the two years in which readings were taken in March, the
difference in the volumes evaporated inside and outside the
wood in that month was less during equal periods than in June,
with the exception of one day.

1 Livingston, The Plant World, 1915.

128

THE BOTANY GARDENS

3. Light intensities in the wood.

In making these experiments the Wiesner photometric method
has been adopted and an exposure meter used. The time taken
for a piece of sensitized paper to acquire the standard tint is
observed in:

1 . Bright diffuse light at the beginning of the experiment.

2. Bright diffuse light at the end of the experiment.

3. The wood (a) under the oaks; (b) under the ash trees;

(c) under the willows.

The observations are made as soon after mid-day as possible,
generally at 12.30 (sun time). In each case the mean of three
readings is taken. The average of the two results for bright
diffuse light (x) is compared with the results under the oaks or
ash or willows (y). The light intensity is in inverse ratio to the
time taken for the paper to acquire the standard tint.

The ratios may be expressed either, as Wiesner expresses
them, as the light intensity (at time of observation) under the

trees as a fraction of that in the open ( - ), or, as Salisbury ex-
presses them, as the light intensity under the trees as a percentage
of the light outside the wood, (-x 100), e.g. if the photographic

paper takes 2 seconds under the trees and i second outside to
reach the standard tint, it may be expressed as \ or 50 per cent.
The experiments to find the intensity of light under the trees
in the J.A.G.S. wood have extended over a period of thirteen
years. They have been made by girls in the dinner-hour. As
a rule there are no records in April owing to the Easter holidays.
The observations in the wood have been made from the same
places under oaks, willows, and ash trees.

1919. COMPARISON OF LIGHT INTENSITIES UNDER OAKS AND
WILLOWS AND LIGHT INTENSITY OUTSIDE THE WOOD

Date

Time

Under Oaks

Under Willows

May 21

12.30 (sun time)

50 per cent.

27 per cent.

3

5>

40

14

June 6

J>

397

13

July 31

10.30

28

ii

Oct. 7

12.15

33'3

16

28

J>

50

14

Nov. 25

J)

63-6

58

(Photo. II. Drake)

FIG. 34. The Dell and Atmometer. 1919. Label showing place where
light intensity was noted under Willows

THE WOODS

129

1926. COMPARISON OF LIGHT INTENSITIES UNDER ASH TREES
AND LIGHT INTENSITY OUTSIDE THE WOOD

Date

Time

Percentage

May 6

12.30 (sun time)

70-8

II

60

13

58-3

27

25

28

25

Ju

ne 10

21-4

ii

18-2

21

15

22

8-75

LIGHT INTENSITIES UNDER OAKS IN VARIOUS YEARS SHOWING
THE DECREASE WITH INCREASING THICKNESS OF CANOPY

Tear

Dates

Ai

WL

lit

1921
1926
I93i

June 7, 13, 28
June 10, n, 21, 22
June 2, 8, 15, 22

Average light intensities inside

wood shown as percentages of

light intensities outside wood

at the same time

21-4
i i'i
6-97

The above years have been chosen as owing to the range of dates on which
the readings were taken a fair average for the month could be calculated.

LIGHT IN THE WOOD AS PERCENTAGES OF LIGHT IN THE OPEN
IN LIGHT PHASE AND SHADE PHASE

Tear

Date

Locality in wood

Percentage of
light outside
wood

1926

J>

March 26 (light phase)
June 21 (shade phase)

Under willow trees

)5

61-7

7'7'

\ The shade phase has probably not reached its maximum, compare the July
record on p. 128.

Simple light intensity experiments made by younger girls.

The experiments described above have been made by girls of
Form VI, specializing in science, but in recent years the children
of the two forms who had charge of the wood (average age, 12)
made their own light intensity experiments with pieces of
photographic paper.
The girls stood out in the open, or in various parts of the wood,

4158 s

1 30 THE BOTANY GARDENS

some under oak trees, others under ash trees. At a given signal
(a whistle was blown) the pieces of photographic paper were
produced from books, and exposed at arm's length. At another
signal the papers were covered, brought into the laboratory,
and fixed in hypo.

Some striking series were obtained, the paper from the open
almost black, that from under the oaks very pale, and a medium
tint under the ash trees.

PLANTS OF THE NEW WOOD AT J.A.G.S.

TREES OF THE MAIN PART.
Common or Pedunculate Oak
Ash
Goat Willow

SHRUBS AND SMALL TREES.
Bramble
Common Hazel
Wild Rose
Hawthorn
Honeysuckle
Ivy
Maple
Dogwood
Spindle
Guelder Rose
Gean

Crab Apple
Wild Service Tree
Wayfaring Tree
Common Birch
Hairy Birch
Sloe

Hornbeam
White Beam Tree

HERBS.
Bluebell
Dog's Mercury
Yellow Dead-nettle
Primrose
Lesser Celandine

Quercus robur (pedunculata) (d) l

Fraxinus excelsior (l.sd.)

Salix caprea (f)

Rubus fruticosus (d)

Corylus Avellana (a)

Rosa canina and arvensis (d)

Crataegus Oxyacantha (d)

Lonicera Periclymenum (d)

Hedera Helix (a)

Acer campestre (f)

Cornus sanguined (f)

Euonymus europaeus (f)

Viburnum Opulus (o)

Prunus avium (o)

Pyrus Mains (o)

Pyrus torminalis (o)

Viburnum Lantana (o)

Betula alba (o)

Betula pubescens (o)

Prunus spinosa (o)

Carpinus Betulus (r)

Pyrus Aria (r)

Scilla non-scripta (l.d.)

Mercurialis perennis (l.sd.)

Lamium Galeobdolon (l.sd.)

Primula vulgaris (a)

Ranunculus Ficaria (a)

1 Symbols as in Tansley's Types of Vegetation: (d) = dominant; (l.sd.) = locally
subdominant; (/) = frequent; (o) = occasional; (r) = rare; (a) = abundant;
(/./.) = locally dominant.

o

I

3

.5

O

THE WOODS

PLANTS OF THE NEW WOOD AT J.A.G.S. (continued)

HERBS (continued).
Wood Anemone
Enchanter's Nightshade
Pink Campion

Cuckoo-flower or Lady's Smock
Common Speedwell
Germander Speedwell
Hairy Wood Rush
Bush Vetch
Wild Strawberry
Bugle

Greater Stitchwort
Herb Bennet
Wild Garlic
Wood Sage
Barren Strawberry
Wood Violet
Wild Arum
Ground Ivy
Wild Angelica
Wood Sanicle
Wood Sorrel
Wood Spurge
Wood Buttercup
Figwort
Woodruff
Tway-blade
Foxglove
Wood Pimpernel
Forget-me-not
Lady Fern
Hard Fern
Polypody
Oak Fern
Bracken

Green Hellebore
Early Purple Orchid
Spotted Orchid
Golden Saxifrage
Lily-of-the-Valley
Butcher's Broom
Herb Paris

Anemone nemorosa (a)

Circaea lutetiana (a)
Lychnis diurna (Melandrium rubrum) (a)

Cardamine pratensis (a)

Veronica officinalis (a)

Veronica chamaedrys (a)

Luzula pilosa (a)

Vicia septum (a)

Fragaria vesca (f)

Ajuga reptans (f)

Stellar ia Holostea (f)

Geum urbanum (f)

Allium ursinum (f)

Teucrium Scorodonia (f)

Potentilla Fragariastmm (f)

Viola Riviniana (f)

Arum maculatum (f)

Nepeta Glechoma (f)

Angelica sylvestris (f)

Sanicula europaea (f)

Oxalis Acetosella (f)

Euphorbia amygdaloides (o)

Ranunculus auricomus (o)

Scrophularia aquatica (o)

Asperula odorata (o)

Listera ovata (o)

Digitalis purpurea (o)

Lysimachia nemorum (o)

Myosotis sylvatica (o)

Athyrium Filix-foemina (o)

Blechnum Spicant (o)

Polypodium vulgare (o)
Polypodium (Phegopteris) Dryopteris (o)

Pteris aquilina (o)

Helleborus viridus (o)

Orchis mascula (o)

Orchis maculata (o)

Chrysosplenium oppositifolium (r)

Convallaria majalis (r)

Ruscus aculeatus (r)

Paris quadrifolia (r)

APPENDIX

Percentage of water in plants. For many years the percentage of
water in plants, or parts of plants, has been found each year.
Experiments are often made on leaves. The leaves have been
obtained from the garden, dusted, weighed, and heated in a water-
oven and weighed again. This heating has been repeated until the
weight was constant. The percentage of water has been found in the
leaves of forty-one genera. Usually a number of girls test leaves of
the same plant, and the results are compared and recorded.

The percentage in leaves of different genera has varied from 60 to
89; in the great majority of leaves it was between 70 and 80. The
percentages of water in whole plants, twigs, buds, bulbs, tubers,
fruits, and seeds have also been found.

The percentages of water found in Brussels Sprouts in one year
were 88-2, 88, 88, 88, 87-9, 87-8, 877, 87, 86-9, 85-9, 85-09 average
87-32; in the next year they were 87-04, 85-5, 85, 85, 84-7, 84-3,
84 average 85-08.

Weight of ash. After the leaves, or other parts of plants, had been
dried they were strongly heated over a bunscn flame until no dark
matter was left. Sometimes, as in the case of leaves, small baking
tins (costing a penny each) were used instead of crucibles, as crucibles
hold so little, and any error in weighing such small quantities would
be larger in proportion. Sometimes crucibles were used for other
parts than leaves, and occasionally the oven-dried portions of plants
were heated strongly in hard glass test-tubes.

In all cases the ash formed was weighed, and heated again until
the weight was constant. In a great many cases the weight of ash
produced after the plants, or parts of plants, had been strongly
heated was less than 3 per cent, of the original weight.

Weight of ash in potato tuber was 1-07 per cent, of original weight of tuber.
Weight of ash in maize grain was I -2 per cent, of original weight of grain.

Analysis of ash.

Test for sulphates. If a solution of ash in water is filtered, the
filtrate acidified with hydrochloric acid and barium chloride added,
a white precipitate is formed, indicating the presence of sulphur in
the form of a sulphate.

Test for phosphates. If an equal bulk of concentrated nitric acid
is added to a small portion of ash solution, and then excess of ammo-

APPENDIX 133

nium molybdate, a yellow precipitate, on boiling, indicates the
presence of a phosphate.

Test for sodium. If a clean platinum wire, which has been dipped
into hydrochloric acid, is put into some plant ash arid then held in
a non-luminous flame, a yellow colour indicates the presence of
sodium.

Test for potassium. If a clean platinum wire, which has been
dipped into hydrochloric acid, is put into some plant ash and then
held in a non-luminous flame, arid the flame viewed through blue
cobalt glass, a reddish-violet coloration is seen, indicating the presence
of potassium.

Iodine solution. Make a strong solution of potassium iodide in
distilled water, and add to it crystals of iodine. Dilute this solution
with distilled water to a light-brown colour.

A deep sink. A deep sink is a great convenience in a laboratory.
In it potometers and other apparatus used in transpiration experi-
ments can be fitted up under water. A tap well above the sink
allows tall jars, such as those sometimes used in water-culture
experiments, to be washed easily.

TRANSPIRATION. READINGS OF POTOMETER UNDER VARYING

CONDITIONS

The following readings were taken when a twig bearing twenty-
seven leaves was inserted in a potometer (Farmer's) .

External conditions

Distance in tube
along which
water receded

Time
(in seconds]

Average

Sunshine and breeze

2 cm.

ro

14

12

12-4

13

13

Shade and slight breeze

2 cm.

26

30

30-6

36

No light

2 cm.

274

212

221-3

I 7 8

134

APPENDIX

TO SEE IF THERE IS A RISE IN TEMPERATURE DURING
RESPIRATION. WHEAT GRAINS

Date

Temperature of
living grains

Temperature of
dead grains

Difference

O /""I

L(.

C.

C.

Jan. 22
23

I5-5
16

14
I4-5

i'5
i'5

24

25
28

14-5
16

17*5

13
14

!5

i'5

2

2'5

29

17-5

15

2'5

Auxanometer. A supply of sheets of paper the right size and
gummed at one end can be obtained for the drum. The paper can
be blackened by holding it in the smoky flame of a gas jet, but it is
better to use the flame of burning camphor.

Test for grape sugar (glucose). Make a solution of grape sugar,
and boil it in a test-tube with some Fehling's solution. A red pre-
cipitate is formed.

Test for cane sugar if grape sugar is absent. Boil a solution for
a few minutes with dilute hydrochloric acid. (The cane sugar is
changed into grape sugar.) Neutralize with caustic soda or potash.
Add Fehling's solution and boil. A red precipitate is formed.

Test for cane sugar if grape sugar is present. Put equal quantities
of the solution to be tested into two test-tubes of about equal
diameters, (i) Add a measured volume of Fehling's solution to one
test-tube and boil contents. (2) Add a little hydrochloric acid to the
contents of the other test-tube, boil contents, and neutralize with
caustic soda or potash. Add the same volume of Fehling's solution
as in (i) and boil. If solutions in (i) and (2) are boiled for the same
length of time after Fehling's solution is added, the amounts of
precipitates can be compared and a roughly quantitative result
obtained.

APPENDIX
STORAGE OF FOOD IN PARTS OF PLANTS

135
OTHER THAN SEEDS

Plants

Organ

Iodine test

Fehling's
solution test

Beetroot
Carrot

Root
Root

Slight blue-black
colour in small

Red ppt.
Red ppt.

area

Parsnip

Root

Blue-black colour

Red ppt.

Turnip

Ilypocotyl

Slight blue-black
colour in small

Red ppt.

area

Iris

Rhizome

Blue-black colour

Red ppt.

Solomon's Seal
*Apple
* Grape

Rhizome
Receptacle
Pericarp of
fruit

Red ppt.
Red ppt.
Red ppt.

* Tomato

Pericarp of
fruit

Red ppt.

Nature of food

Grape sugar

fA little starch

Grape sugar

/Starch
| Grape sugar
f A little starch
j^Grape sugar

f Starch

\Grape sugar
Grape sugar
Grape sugar
Grape sugar

Grape sugar

* Sugar is not a food reserve in these fruits.

INDEX

Absorption of water,

by root, 4;

by moorland plants, 95 ;

by salt marsh plants, 102.
Acorns,

age of trees bearing, 122;

germination of, 113, 123.
Anaerobic respiration, 34.
Animal life,

in lane, 79;

in pond, 91 ;

in wood, 124.
Ash of plants,

analysis of, 16, 132;

weight of, 1 6, 132.
Atmorneter, 127.
Auxanometer, 37-9, 134.

Bogs,

construction of, 83, 87, 96, 97;
plants of, 97, 98.

Carbon dioxide,

evolution of, 2830;

and starch formation, 1 1 .
Chalk beds,

construction of, no;

plants of, no, in.
Chlorophyll and starch formation,

13-

Climbing plants, 71-4, 77, 78.
Clinostat, 43, 44, 47.
Cornfield, 107-8.
Culture solutions,

bacterial, 116;

water-, 16-21, 116.

Diastase, 4, 14.
Diseases,

of seedlings, 20;

of trees, 125.

Elements of plants, 16, 18.
Etiolated plants, 6, 7.
Evaporating power of the air, 127.

Flowering, time of, 78.
Food substances,

storage of, 3, 135;

tests for, 3, 134.
Freshwater marshes, 83;

plants of, 86, 87.

Germination, conditions of, 1-3.

Gravity, influence of,

on direction of growth, of root, 43 ;

of stem, 45, 46;
perception of, 44-6.
Growth,

distribution of, in root, 35, 36; in

stem, 35, 37;
direction of, in root, 39, 40, 43; in

stem, 40, 41, 46;
influence of light on, 5, 42;
measurement of, 37-9.

Heath,

construction of, 93 ;

plants of, 93-6.
Humus, 53, 106, 126.

Insects, observations of visits of, 65-

70.
Iodine, solution of, 133.

Labels, 58.
Lammas shoots, 123.
Lane,

construction of, 75, 76;

plants of, 79-81.
Leaf structure, 24.
Light, influence of,

on germination, 2 ;

on growth of seedlings, 5 ;

on direction of growth, 40-2.
Light,

perception of, 42 ;

and starch formation, 10.
Light intensities, 12830.

Manures,

effect of absence of, 1 1 6 ;

effect of artificial, 1 16-18.
Marshes, see freshwater marshes and salt

marshes.

Meadow, 108-10.
Mechanical analysis of soil, 48.
Mendelian experiments, 113-15,
Microscope, use of, 23.
Moll's experiment, 12.
Mycorrhiza, 17, 93.

Nitrates, influence of, on leaf develop-
ment, 1 1 6.

Oxygen,

absorption of, 30.
evolution of, 12, 13.

138 INDEX

Paths,

round ponds, 83, 85;

plants of, 87, 88.
Peat bogs, see bogs.
Pebble beach,

construction of, 1046;

plants of, 1 06.

Permeability of soils to air, 52.
Photosynthesis, 8-15.
Pollination,

experiments on, 60-5;

of primrose, 64.
Ponds,

construction of, 82-5;

plants of, 85, 86.
Pores in leaves, 23.
Potometer, 25-7, 133.

Reports on work, 58.
Reproduction,

of water plants, 88.

of sand dune plants, 100.
Respiration, 28-34, 134.
Respiratory coefficient, 31.
Respiroscope, I.

Sachs' solution, 17.
Salt marshes, 101-4;

plants of, 87, 104.
Salt solution, 101, 103.
Sand dunes,

construction of, 99;

plants of, i o i .
Self-pollination,

records of, 62 ;

in annuals, 63, 64.
Sink in laboratory, 26, 133.
Soil, experiments on, 48-54, 79, 115.
Starch,

conditions of formation of, 9, 10-14;

conversion into sugar of, 14;

records of, 3, 8, 9, 135.
Starch prints, 10, n.
Stomates, 24;

of salt marsh plants, 102.
Struggle for existence, 112.
Sugar, presence of,

in leaves, 9;

Sugar, presence of (contd.}
in other parts, 135;
tests for, 134.

Tools, care of, 57.
Temperature,

and germination, 2 ;

and oxygen production, 13;

and respiration, 33, 134.
Temperatures,

in pond, 89-91;

of soil, 54, 79;

in woods, 126.
Transpiration,

demonstration of, 22 et seq.;

rate of, 25-8, 133;

of heath plants, 95;

of salt marsh plants, 101.
Transpiration and absorption, 27.

Variation, 1 12.
Visitors to gardens, 58.

Wall,

construction of, 1 1 1 ;

plants of, 112.
Water,

path in stem, 5;

influence on direction of growth, 39;

percentage in plants, 16, 132;

percentage in soil, 48;

of moorland soil, 95;

of salt marshes, 1 02 ;

rise of, in soil, 502.
Water capacity of soils, 52.
Water-cultures, 16-21, 116.
Water supply,

of bog, 97;

of ponds, 82, 83, 85;

of salt marshes, 101, 103.
Weeds, competition of,

in heath, 94;

in wood, 121.
Woods,

changing conditions of, 12530;

construction of, 119-20;

ground flora of, 121;

plants of, 1 30 , 1 3 1 ;

thinning of, 124.

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