the formation of vegetable mould-第6章
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other parts。 When fresh leaves were given in the evening to worms
kept in confinement and examined early on the next morning；
therefore not many hours after they had been dragged into the
burrows； the fluid with which they were moistened； when tested with
neutral litmus paper； showed an alkaline reaction。 This was
repeatedly found to be the case with celery； cabbage and turnip
leaves。 Parts of the same leaves which had not been moistened by
the worms； were pounded with a few drops of distilled water； and
the juice thus extracted was not alkaline。 Some leaves； however；
which had been drawn into burrows out of doors； at an unknown
antecedent period； were tried； and though still moist； they rarely
exhibited even a trace of alkaline reaction。
The fluid； with which the leaves are bathed； acts on them whilst
they are fresh or nearly fresh； in a remarkable manner； for it
quickly kills and discolours them。 Thus the ends of a fresh
carrot…leaf； which had been dragged into a burrow； were found after
twelve hours of a dark brown tint。 Leaves of celery； turnip；
maple； elm； lime； thin leaves of ivy； and； occasionally those of
the cabbage were similarly acted on。 The end of a leaf of Triticum
repens； still attached to a growing plant； had been drawn into a
burrow； and this part was dark brown and dead； whilst the rest of
the leaf was fresh and green。 Several leaves of lime and elm
removed from burrows out of doors were found affected in different
degrees。 The first change appears to be that the veins become of a
dull reddish…orange。 The cells with chlorophyll next lose more or
less completely their green colour； and their contents finally
become brown。 The parts thus affected often appeared almost black
by reflected light； but when viewed as a transparent object under
the microscope； minute specks of light were transmitted； and this
was not the case with the unaffected parts of the same leaves。
These effects； however； merely show that the secreted fluid is
highly injurious or poisonous to leaves； for nearly the same
effects were produced in from one to two days on various kinds of
young leaves； not only by artificial pancreatic fluid； prepared
with or without thymol； but quickly by a solution of thymol by
itself。 On one occasion leaves of Corylus were much discoloured by
being kept for eighteen hours in pancreatic fluid； without any
thymol。 With young and tender leaves immersion in human saliva
during rather warm weather； acted in the same manner as the
pancreatic fluid； but not so quickly。 The leaves in all these
cases often became infiltrated with the fluid。
Large leaves from an ivy plant growing on a wall were so tough that
they could not be gnawed by worms； but after four days they were
affected in a peculiar manner by the secretion poured out of their
mouths。 The upper surfaces of the leaves； over which the worms had
crawled； as was shown by the dirt left on them； were marked in
sinuous lines； by either a continuous or broken chain of whitish
and often star…shaped dots； about 2 mm。 in diameter。 The
appearance thus presented was curiously like that of a leaf； into
which the larva of some minute insect had burrowed。 But my son
Francis； after making and examining sections； could nowhere find
that the cell…walls had been broken down or that the epidermis had
been penetrated。 When the section passed through the whitish dots；
the grains of chlorophyll were seen to be more or less discoloured；
and some of the palisade and mesophyll cells contained nothing but
broken down granular matter。 These effects must be attributed to
the transudation of the secretion through the epidermis into the
cells。
The secretion with which worms moisten leaves likewise acts on the
starch…granules within the cells。 My son examined some leaves of
the ash and many of the lime； which had fallen off the trees and
had been partly dragged into worm…burrows。 It is known that with
fallen leaves the starch…grains are preserved in the guard…cells of
the stomata。 Now in several cases the starch had partially or
wholly disappeared from these cells； in the parts which had been
moistened by the secretion； while it was still well preserved in
the other parts of the same leaves。 Sometimes the starch was
dissolved out of only one of the two guard…cells。 The nucleus in
one case had disappeared； together with the starch…granules。 The
mere burying of lime…leaves in damp earth for nine days did not
cause the destruction of the starch…granules。 On the other hand；
the immersion of fresh lime and cherry leaves for eighteen hours in
artificial pancreatic fluid； led to the dissolution of the starch…
granules in the guard…cells as well as in the other cells。
From the secretion with which the leaves are moistened being
alkaline； and from its acting both on the starch…granules and on
the protoplasmic contents of the cells； we may infer that it
resembles in nature not saliva； ｛22｝ but pancreatic secretion； and
we know from Fredericq that a secretion of this kind is found in
the intestines of worms。 As the leaves which are dragged into the
burrows are often dry and shrivelled； it is indispensable for their
disintegration by the unarmed mouths of worms that they should
first be moistened and softened； and fresh leaves； however soft and
tender they may be； are similarly treated； probably from habit。
The result is that they are partially digested before they are
taken into the alimentary canal。 I am not aware of any other case
of extra…stomachal digestion having been recorded。 The boa…
constrictor is said to bathe its prey with saliva； but this is
doubtful； and it is done solely for the sake of lubricating its
prey。 Perhaps the nearest analogy may be found in such plants as
Drosera and Dionaea； for here animal matter is digested and
converted into peptone not within a stomach； but on the surfaces of
the leaves。
Calciferous Glands。These glands （see Fig。 1）； judging from their
size and from their rich supply of blood…vessels； must be of much
importance to the animal。 But almost as many theories have been
advanced on their use as there have been observers。 They consist
of three pairs； which in the common earth…worm debouch into the
alimentary canal in advance of the gizzard； but posteriorly to it
in Urochaeta and some other genera。 ｛23｝ The two posterior pairs
are formed by lamellae； which； according to Claparede； are
diverticula from the oesophagus。 ｛24｝ These lamellae are coated
with a pulpy cellular layer； with the outer cells lying free in
infinite numbers。 If one of these glands is punctured and
squeezed； a quantity of white pulpy matter exudes； consisting of
these free cells。 They are minute； and vary in diameter from 2 to
6 microns。 They contain in their centres a little excessively fine
granular matter； but they look so like oil globules that Claparede
and others at first treated them with ether。 This produces no
effect； but they are quickly dissolved with effervescence in acetic
acid； and when oxalate of ammonia is added to the solution a white
precipitate is thrown down。 We may therefore conclude that they
contain carbonate of lime。 If the cells are immersed in a very
little acid； they become more transparent； look like ghosts； and
are soon lost to view； but if much acid is added； they disappear
instantly。 After a very large number have been dissolved； a
flocculent residue is left； which apparently consists of the
delicate ruptured cell…walls。 In the two posterior pairs of glands
the carbonate of lime contained in the cells occasionally
aggregates into small rhombic crystals or into concretions； which
lie between the lamellae； but I have seen only one case； and
Claparede only a very few such cases。
The two anterior glands differ a little in shape from the four
posterior ones； by being more oval。 They differ also conspicuously
in generally containing several small； or two or three larger； or a
single very large concretion of carbonate of lime； as much as 1。5
mm。 in diameter。 When a gland includes only a
