466 
NMALOURE 
[March 15, 1883 
the same family ; or with the still freer peltate leaves of 
Hydrocotyle; or again with the divided but more broadly 
segmented leaves of those tall open-field species, cow- 
parsnip, Heracleum sphondylium, and Alexanders, Smyr- 
nium olusatrum, which have only to compete against the 
grasses and clovers ; or, finally, with the large waterside 
forms, Apium graveoleus, Stum latifolium, and Angelica 
silvestris. So, too, take the much segmented herb— 
Robert, Geranium Robertianum, of all our hedgerows, 
growing side by side with the like-minded chervils and 
carrots, and compare it with that persistent rounded 
G. molle, &c., but even in many exotic Pelargoniums. 
Among composites the crowded type is best exemplified 
by that thicket weed, milfoil, Achz//ea millefolium, with its 
infinite number of finely-cut, pinnatifid segments ; while | 
in the taller but closely-allied sneezewort, Achillea 
plarmica, growing on high open pastures, we get the 
same general type in outline and venation, only entire 
save for the slight serrations along its edge. In tansy, 
Tanacetum vulgare, also a hedgerow plant, the same 
type as milfoil recurs ona far larger and handsomer 
scale. Compare these with coltsfoot and burdock, or 
even with the tall eupatory and the tufted, close-packed 
daisy. 
group, &c.; while among larger cryptogams the majority 
of thicket ferns display an equally marked subdivision of 
the fronds and pinne. It may be added that highly 
civilised countries like England are particularly rich in 
these subdivided types of foliage, owing to the predo- 
minance of hedgerows and of tall grasses. 
As in the submerged plants, so in the matted terrestrial 
undergrowth, whorling of linear leaves may practically 
answer the same purpose as minute segmentation. 
plants solve the difficulty of catching stray carbon in the 
one way, and some solve it in the other. 
easiest modification of its own ancestral type. For 
example, take the stellate tribe. Their tropical allies, 
the larger Rubiacez, have simple, usually entire, opposite 
leaves, with interpetiolar stipules. 
northern forms however, the interpetiolar stipules have 
grown out into linear leaf-like foliar organs, forming with 
the true leaves an apparent whorl of six members. Some- 
times, too, the whorl is enlarged to as many as eight 
leaves, and sometimes reduced to four. These thick 
whorls of small leaves, always well turned outward to the 
sunlight, have become practically analogous in their 
action to minutely segmented leaflets, in our English 
Galiums, Asperulas, and Sherardia. Two of them at 
least, G. mollugo and G. aparine, are extremely common 
hedgerow plants. Compare them with the broad-leaved 
free-climbing Rubia peregrina, which has only four large 
members to each whorl. 
Among monocotyledons, where (as will be afterwards 
explained) the type is given by the peculiarity of the 
cotyledon and governs the venation, minute subdivision 
is replaced in the matted undergrowth by single, linear, 
lanceolate blades, which answer the selfsame purpose in 
the long run. The grasses, sedges, and woodrushes are 
sufficient examples. 
and narrow, and all with long thin flower stems, strive to 
overtop one another, and run up side by side to a con- | 
They may be compared with the large | 
siderable height. 
rich leaves of the bulbous lilies, tulips, amaryllids, and 
orchids. In both cases the type is the same, but the 
development is different. 
the grasses, as for example ribwort plantain, though 
wholly unlike in type, are apt to be drawn up and assimi- 
lated to them, not merely in general character, but even 
in venation and mode of fertilisation. Other grass-like 
dicotyledons are found among the Polygonums, Armerias, | 
Bupleurums, pinks, &c., all under similar circumstances 
to those of the grasses themselves. 
Other good miscellaneous instances of the weedy | 
type are fumitory, Corydalis, moschatel, the camomile | 
Here the numerous leaves, all long | 
Some | 
Each adopts the | 
In the small, weedy, | 
kinds, such as cabbage and charlock. 
Intermediate types between these two extremes of 
entire obicularity and minute subdivision occur every- 
where. Compare, from this point of view, the common 
meadow buttercups, which grow in fully occupied mea- 
dows, with Ca/tha and the lesser celandine. Compare, 
again, the mallows on the one hand with the peas on the 
other, or the docks with the crucifers. Throughout these 
intermediates, various stages can be easily observed. For 
example, the South European water-chestnut, Zrvapa 
natans, beautifully illustrates the gradations which have 
| finally given us our own Azppuris and Myriophyllum from 
geraniaceous type which recurs, not only in our English | 
an Onagraceous or Saxifrage ancestor. It has a number of 
floating leaves (Fig. 18) supported by bladder-like petioles 
filled with air, and arranged radially round the stem. 
Hence, though large and spreading, they are distinctly 
bilateral, and they do not interfere with one another's 
food supply. But the submerged leaves (Fig. 19, very 
diagrammatic) are mere pinnate skeletons of the venation, 
waving about in the water below. Among monocotyledons, 
the Potamogetons show us some very instructive similar 
cases, altered in character by the peculiarities of the very 
persistent monocotyledonous foliar type. In the floating 
leaves of P. xatans they come as near the waterlilies 
as a monocotyledon can reasonably expect to do; in 
P. pectinatus, the wholly submerged leaves look like 
long blades of grass, proceeding from the thread-like 
stems. 
Less minutely subdivided than the hedgerow plants are 
a large class of somewhat weedy forms, well typified by 
our smaller English crucifers. These are often pinnately 
| divided to a considerable extent, as in Cardamine hirsuta 
and Senebiera didyma. Compare them with the taller 
Much the same 
type reappears in the lowly forms of Papilionacez, as for 
example in Aythyllis, Astragalus, Ornithopus, Hippo- 
crepis, &c. On the other hand, in the tall climbing 
Vicias, and still more in Zathyrus, the leaflets, having 
more carbon, more sun, and less competition, fill out 
rounder, and generally decrease in number, the upper 
ones being transformed into tendrils. But in the very 
grass-encumbered clover-like types, Ovonts, Medicago, 
Melilotus, Trigonella, and, above all, Trifolium itself, 
the leaflets are dwarfed and reduced to three, the lower 
members being suppressed, and only the three terminal 
ones left, so as to raise them on a long footstalk up to the 
air and sunshine. Compare the very similar leaflets of 
wood-sorrel. Again, look at the various conditions under 
which the following Rosaceous plants grow : pear, black- 
thorn, strawberry, cinquefoil, silver-weed, great burnet, 
salad burnet, and compare some of them with clover, 
lady’s-fingers, and Hippocrepis. The comparison tells its 
own tale at once. 
Finally, we must briefly allude to a large class of tufted 
plants, usually with entire, ovate, obovate, or ovate- 
lanceolate leaves, which grow in a rosette from a centre, 
and insure themselves a good supply of carbon and of 
light by keeping under all competitors with their close 
tufts. Of these, our common daisy forms an excellent 
example: notice the tight way it fits itself against the 
ground so as to prevent grass from growing beneath it. 
Another good case in point is Plantago media: compare 
form and habit with those of P. major and P. lanceolata. 
To the same class, more or less, may be referred Avabis 
thaliana and many crucifers, London Pride, the common 
primrose, Hzeracium pilosella, &c. ; and, with more pin- 
| nate, lyrate, or prickly leaves, the young thistles, and the 
Plants that consort much with | 
| 
radical foliage of many ligulate composites. 
The shapes of leaves thus depend upon the average 
surrounding conditions, modifying a given ancestral type. 
How these ancestral types themselves were first deve- 
loped we shall have to inquire in our next paper. 
GRANT ALLEN 
(To be continued.) 
