Jan. 13, 1882.] 



KNOWLEDGE • 



217 



AN ILLitaiBATED 



MAl^lNEoTSOENCE 



PUINl^RJED -EXACTI^ESCRMD 



LOXDOX : FRIDAY, JAXUARY 13, 1882. 



Contexts of No. 11. 



PAGE. 



A Winter Weed. Bv Grant Allen 217 

 Precession of the Equinoxes. By 



the Editor 218 



Nights with a 3-inch Telescope 220 



Found Links. By Dr. Andrew 



Wilson, F.L.S., ic— Part II 222 



Fallaeies about Luck. By the Editor 222 

 The Principle of the Ve'mier. By 



J. R. Campbell 224 



Colours of Aoimjils 22i 



Zodiacal Map 225 



The Pvnumd of Meydoom. Bv 



Amelia B. Edwards '.. 221 



Vegetable Poisons 226 



The New Star in Cassiopeia 227 



Actinium; a Metal found in White 



Zinc Pipment 227 



Fossils in Meteoric Stones 227 



Duration of Life 228 



Knowledge for the Young 229 



COBBBSPOSDBXCB 229-233 



Queries 234 



Replies to Queries 2.35 



Answers to Correspondents 236 



Notes on Art and Science 237 



Our Mathematical Column 238 



Our 'Whiat Column 239 



Our Chess Column 239 



A WINTER WEED. 



Bv Grant Allen. 



A DAY or two of warm weather, wafted to us by the 

 westerly breezes, has brought out the daisies on the 

 lawn as vigorously as if it were ilay, instead of January. 

 The sward is dappled all over with their little timid white 

 blossoms in a way that quite defies the decencies of the 

 season. The fact is, modest and shrinking as they seem to 

 be, daisies are very hardy and hard-working small plants, 

 which never miss an opportunity of pushing their way in 

 the world ; and no doubt they have their reward, for 

 probably no other flowering kind, except, perhaps, one or 

 two grasses, have been lialf so successful in colonising the 

 fields and hill-sides as these unobtrusive, wee things liave 

 been. In the spring, they are the very earliest plants to 

 bloom ; and since the early flower catches the bee, they 

 begin setting their seed before the other blossoms are well 

 awake ; all tlirough the summer and autumn they go on 

 blooming uninterruptedly ; and even when winter comes, 

 they are readj' at a moment's notice to take advantage of 

 any brief gleam of sunlight which may happen to occur, 

 putting forth their pretty buds fearlessly, and alluring the 

 last stray insects of the season to visit their tiny golden 

 bells. 



Here in my hand I have grubbed up one entire daisy- 

 plant, root and all, with my cane ; and when one comes 

 to look closely at its structure, the secret of its success 

 in life is not ditficult to decipher. In the first place, 

 there are the leaves. These we seldom notice when we 

 are examining a daisy, because they are so very retiring 

 and unobtrusive. They lie flat upon the ground, in a 

 small, round, spreading rosette, pressed as tightly as pos- 

 sible against the soil beneath. That is one of the tricks by 

 means of which the daisy secures itself a place in the world. 

 It grows generally in open pastures and commons covered 

 with grass ; and as the grass tends always to raise its tall 

 blades as high as possible, the daisy' might easily be over- 

 shadowed by that powerful competitor. Now, there are two 

 ways in which diflferent plants li\-ing in such circumstances 

 can avoid being elbowed out of existence. One way is by 

 sending up taller and bigger leaves than the gi-asses, so as 



to intercept the air and sunlight ; and this is the plan 

 adopted by sucli weeds as dock, burdock, coltsfoot, and 

 some plantains. As a rule, however, such tactics can only 

 be followed by plants which possess a reserve fund of food- 

 stutls laid by in their roots or stocks, for otherwise the 

 young leaves would be choked and starved before they 

 could gi-ow high enougli to overtop tlic competing grasses. 

 Or, to put it more definitely, those kinds alone have suc- 

 ceeded in this way which happened to devclope both large 

 leaves and rich reserves of starcli at one and tlie same time. 

 The second plan is tliat followed by the daisy, the hoaiy 

 plantain, and many other field-weeds. These plants have 

 learnt to press their foliage closely down in a little circle 

 upon the ground, so as to prevent any grasses from grow 

 ing up around them and intercepting the sun and air. In 

 other words, such individuals among them as happened to 

 display this tendency, in a slight degree, survived tlie best ; 

 and among their descendants, such as can-ied it out further 

 and further, spread most afield, while such as fell short of 

 the desired quality, got killed oflT young by neighbouring 

 weeds. Thus, at last, the daisy acquired its present suc- 

 cessful haljit of gi-owing close to the ground, and so check- 

 ing competition in the bud, or rather in the very seedling. 



But why, it may be objected, do not all other plants do 

 the same ? The answer is, because all are not adapted for 

 the same sort of life as the daisy. One kind survives in 

 virtue of one point of vantage, another kind survives in 

 \'irtue of another. The English meadow plantains are three 

 closely-allied types of weed, hardly diflfering from one 

 another in any essential point ; yet each of them has solved 

 this problem of foliage in a separate way. The great 

 plantain sends up big, liroad leaves on longish stalks, some- 

 thing like those of garden lettuce, which overtop most of 

 its neighbours ; the lioary plantain spreads a little tuft 

 close to the earth, like the daisy ; and the ribwort plantain 

 meets the grasses on their own ground, by reducing its 

 leaves to mere long, thin, lance-like blades. In each case, 

 the explanation must be accepted on its own merits, with- 

 out prejudice to different explanations elsewhere. The forms 

 of leaves, indeed, are among the most difficult problems of 

 botany, and it must not lie supjjosed that we can account 

 for them all at once by a single simple and easy formula. 

 One might as well ask why the rabbit is not as big 

 as the red deer, or why the fox is smaller than the lion. 

 Each fills its own niche in nature ; so each has been 

 developed into exact correspondence with that particular 

 niche and no other. And different means often subserve 

 exactly tlie same end. The fleetness of the hare is produced 

 by quite other adaptations than the fleetness of the stag ; 

 the foliage of the daisy succeeds by being compact and 

 rounded, the foliage of the buttercup by being cut up into 

 numerous small divergent segments. In short, whatever 

 accidental habit happens to give a plant or animal any 

 advantage in the struggle for e.xistence is perpetuated in its 

 descendants, and gradually perfected by natural selection, 

 and thus the mo.st diverse means often lead up in the long 

 run to the same end. 



The reason why the daisy is able to send up buds and 

 blossoms at a moment's notice seems equally clear. The 

 buds are always l}"ing by in readiness close to the little 

 perennial tufted stock. I cut it down the middle with my 

 pocket-knife, and see, in tlie centre of the tuft, there are 

 two or three unopened flower-buds even now lurking un- 

 seen and waiting for their turn to appear. Practically 

 speaking, the daisy is an evergreen, for it always has 

 green leaves upon it all the year round ; and these green 

 leaves are perpetually engaged, summer and winter, in 

 manufacturing starch from the carbonic acid of the air, 

 which starch is at once laid by in the root-stock to feed 



