10 



• KNOWLEDGE • 



[July 4, 1884. 



THE EVOLUTION OF FLOWERS. 



By Grant Allen. 



some higher lilies. 



ALL the true lilies with which we have dealt so far 

 have had bulbs to grow from, and have been, on the 

 whole, very succulent and herbaceous in character. They 

 have also persisted in the primitive lily habit of producing 

 dry capsules, each of the three cells in which contained 

 numerous seeds. 



There are, however, some higher types of lily, not very 

 largely represented in our British flora, which differ con- 

 siderably from the tulip, the frilillary, and the tiger-lilies 

 in one or other of these central characteristics. I propose 

 briefly glancing at two of these to-day, the common aspara- 

 gus {Aspararjus officiimUn)a.odthe butcher's broom (Emeus 

 aculeatus). They are our two English representatives of 

 the sub-order of Liliacere known as Asparageie. 



Dismiss from your mind entirely the ordinary garden 



Fig. 1. — Asparagus Officinalis. 



notion of asparagus, as a thick, stumpy, succulent shoot, 

 and try to realise the life of the wild plant itself as it 

 grows by the sandy, tideless levels of the Mediterranean, 

 or far more sparingly on a few isolated rocky headlands of 

 our own Cornish or Irish coast Essentially a maritime 

 weed, the wild asparagus has, instead of a bulb, a deep 

 creeping root-stock, buried far out of harm's reach in the 

 sand or the crannies ; and from this stock it sends up every 

 spring a few soft, scaly, annual shoots, thin and wiry, which 

 branch out afterwards into tufted feathery heads of minute 

 foliage. In our gardens, we trench and manure the selected 

 and cultivated variety, so that each year the annual stems 

 grow very large, high, and bushy, and collect abundant 

 material for the next spring's growth, which they conceal 

 during the winter in the buried root-stock. Hence the 



young shoots in the garJen kind have become unnaturally 

 large, thick, and luscious. But in the wild state, asparagus 

 seldom attains more than one quarter the height of the Ijig, 

 luxuriant, cultivated variety, and its spring shoots are far 

 thinner, stringier, and more woody in texture. 



On the edible young stems of the garden asparagus, 

 everybody must have noticed a few short, stumpy scales, 

 generally of a faint mauve colour ; and these are almost 

 the only true leaves the plant ever produces. When it 

 grows older, the place of foliage is fulfilled by the fine 

 clustered hair-like green points, which are, ia fact, very 

 small branches, or, if you like to be extremely scientific, 

 abortive pedicels (that is to say, flower-stalks whose buds 

 and blossoms have never developed). Look very closely 

 at the base of each such cluster — the full-grown garden 

 asparagus will do quite as well for this purpose as its wild 

 ancestor — and you will see that it is enclosed by very tiny 

 dry scales, each of which is really a bract or leaf, s-imilar ta 

 those on the spring shoots. From the axils or angles made 

 by these bracts with the stem, the cluster of abortive 

 pedicels springs, just as each separate blossom in a wild 

 hyacinth or a common spotted orchis, springs from a small 

 bract of a far more conspicuous character. One may say, 

 in fact, that each cluster of so-called leaves in the asparagus 

 answers to a whole head of flowers in the bluebell or orchis, 

 only that the actual blossoms themselves are in this case 

 never developed. 



Why the asparagus has thus taken to producing these 

 innumerable pedicels instead of true leaves would be a long, 

 and diflicult question to answer fully. It must suffice here 

 to say briefly that in many plants of dry places (for example, 

 in the stonecro])s) the stem and branches as well as the 

 leaves are filled with chlorophyll, and help to perform the 

 foliar functions. In others (for example, in the cactuses) 

 the true leaves have dwindled away absolutely to nothing^ 

 because the succulent stem performs their functions better 

 under its own peculiar circumstances. In asparagus, the 

 true leaves remain only as protective scales, but the work 

 of foliage has been taken on by the stem and pedicels, 

 simi)ly because they could do the work more conveniently. 



The flowers of the asparagus are small and greenish, and 

 at first sight very inconspicuous. On looking closer, how- 

 ever, you will see that they are perfect little lilies, each with 

 six distinct perianth-pieces — that is to say, three sepals and 

 three petals, the distinction being here well marked — and 

 the usual six stamens and three-celled ovary. INIany of 

 the flowers, however, have stamens only : others have pistils 

 with abortive stamens : the plant is just beginnini; to 

 separate the sexes in distinct blossoms. But the separation 

 has not yet gone far ; none of the female flowers have as 

 yet quite lost their stamens, though they are reduced to 

 useless filaments bearing abortive anthers. Indeed, a few 

 blossoms on each plant usually still retain both stamens 

 and pistil. Unattractive as they are in colour, the aspa- 

 ragus flowers have a delicate perfume, and secrete abundant 

 honey ; hence they are visited and fertilised by hive bees- 

 and a few other insects. 



But tlie most marked peculiarity about the asparagus, as 

 distinguished from the other lilies we have hitherto ex- 

 amined, is certainly the fact that it produces red berries, 

 instead of dry green or brown capsules. This berry has, 

 of course, been produced, like all others, by the interven- 

 tion of birds, which thus distribute the seeds in the best 

 possible situations. Accordingly, the plant is able to lessen 

 the number of seeds in each cell to one only. To be sure, 

 the flower has two ovules or young seeds in each cell of the 

 ovary ; but as the fruit ripens, one of these usually becomes 

 abortive. This is just the exact reversal of what we saw 

 happen in an earlier stage of evolution ; and yet it is only 



