Aug. 22, 188-t.] 



♦ KNOWLEDGE 



147 



AN ILLUSTRATED ~ 



MAGAZINE OF SCIENCE 



J^^YWORDED-EXACTLYDESjl^ 



LONDON: FRIDAY, AUG. 22, 1884. 



Contents op No. 147. 



PAGE 



Sunflowers. By Grant Allen 147 



A Stranfje Disorder 148 



Paradoxistsin America. By Kiehard 



A. Proctor 148 



Tncycles in 18S4 : Small v. Large 



Wheels and Two-Speed Gearings. 



By John Browning 119 



The Earth's Shape and Motions : 



II. The Diurnal Motion of the 



Stars. {lUu^.) By R. A. Proctor l.=;o 

 Electro-plating. X. By W. Slineo 151 

 Dreams. VII. Bv Edward Clodd l.'>:; 

 The Workshop at "Home. {IUu».) 



By a Working Man 153 



The Greely Expedition. By Andrew 



McPherson 156 



167 



A Xew Volcano 



The WfRtinghoase Brake. {lUut.) 



By " Trevilhick " 157 



Other Worlds than Ours. By M. 



de Fontenelle. With Notes by 



Richard A. Proctor 160 



International Health Exhibition, 



XIII. [IUuk) 161 



British Seaside Resorts. III. By 



Percy Russell 162 



Editorial Gossip IfH 



Mi&cellanea 165 



Correspondence -. The Sense of 



Taste — Perspective — Wearing the 



Dead — A Coincidence, &c 166 



Our ChesB Column 168 



SUNFLOWERS. 



By Grant Allex. 



IT is well to choose a text which everybody can easily 

 verify for hiaiself; and as hardly a house is now 

 without a sunflower, I may as well choose that fashionable 

 blossom as the subject for this morning's discourse. Take 

 down one from the drawing-room mantel-shelf, and you will 

 be able to follow for yourselves what I have to say to you. 

 You had better choose a blossom in which the central 

 florets have not yet begun to open, as you will then be 

 able to fiud flowers in every stage of development. 



The sunflower, I need hardly say, is a member of the 

 composite family ; and each head is not, of course, a single 

 separate flower, but a whole collection of hundreds of 

 golden bells. If you pull out one of these, you will find 

 it consists of a yellow tubular flower, five-lobed above, and 

 bulging broadly at its base. This flower surmounts a large 

 seed, or rather fruit, with one or two wings at its top, 

 which are all that now remain of the original calyx. 



In the centre of the compound flower-head you will find 

 a mass of unopened flower-buds, each one covered and 

 protected by its own scaly bract. These bracts are the 

 remnants of the little leaves which once grew under each 

 blossom when the ancestors of the sunflower still possessed 

 long spikes of flowers. But in course of time the compo- 

 sites learnt to flatten out their spike into a broad, disc like 

 head. Still, however, the bracts, in a much-dwarfed form, 

 remained to separate the individual little bells ; and in 

 some cases, as in the sunflower, they have been utilised for 

 a new purpose — namely, to protect the unopened flower- 

 buds from insects which might otherwise eat them, or lay 

 their eggs upon them. Many composites still retain the 

 bracts ; in others, and often in closely allied forms, they 

 are wanting, having been gradually lost by disuse. There 

 are none in the daisy or the dandelion. 



Beyond this central region, where the buds are yet 

 unopened, you will find two or three rows of newly -opened 

 flowers, with all their lobes displayed, and wi'h the little 



black stamens standing up conspicuously in their midst. 

 These florets are in their first or male stage. If you open 

 carefully with a needle the tube formed by the united 

 stamens, you will find inside the little style, with its two 

 branches still pressed closely together. The bee hovering 

 over these florets in the first state, dusts himself over viitli 

 pollen from the yellow tips of the atithers. This he after- 

 wards carries away to fertilise the other florets. 



Outside the rows of flowers in the first male state we 

 come to some other and more crowded rows, which have 

 reached the second or female cone ition. In them the style 

 has grown longer, so as to overtop the now withered 

 stamens. At the same time, its branches have opened out- 

 ward, and now curl over gracefully, so as to expose their 

 sensitive surfaces. If you look closely you can see, even 

 with the naked eye, grains of pollen cHnging to their 

 surface. 



Outside these female florets again come a few rows of 

 fully-fertilised and over-blown blossoms, which are crowded 

 together by pressure from within, and of which the bees 

 and other visitors hardly take th^ slightest notice. 



Lastly of all, on the very outside of the great compound 

 flower-head, we reach the big expanded golden ray florets, 

 which are, in fact, neuter members of this organised floral 

 community. Their business is to make as large a display 

 as possible, and so to attract insects to the fertile florets iu 

 the centre. If you pull out one of them carefully, you will 

 find that it is tubular in its lower portion, but that the 

 broad upper p.irt is formed by the splitting open of the 

 tube on the inner side. One may still observe faint traces 

 of the original five hibes even in these very enlarged and 

 distorted florets, e.^pecially at the tip, where they are often 

 notched or divided. In some composites the expanded ray 

 florets still keep their styles ; but in the sunflower they 

 have become wholly abortive. We may thus compare the 

 compound head in some respects with a hive of bees con- 

 taining females, males, and neuters. 



It will be observed that the sunflower opens from with- 

 out inward, and the bee who approaches it visits it in the 

 same order. Thus he comes in contact first with the 

 florets in the female stage on the outside, and dusts them 

 over with pollen which he brought from the last head. He 

 then proceeds to the inner rows of male florets, from which 

 he unconsciou^^ly collects pollen to carry to some neigh- 

 bouring plant If either the sunflower or the bee reversed 

 this proceeding, the result would be that the florets would 

 get fertilised with pollen from their own brother flowei-s, 

 the least desirable form of cross-fertilisation ; but here, as 

 elsewhere, natural selection has adapted the habits of the 

 plant to those of its regular visitors, and has thus secured 

 the best form of impregnation. Bees are jiarticularly fond 

 of the sunflower, and obtain from it large quantities both 

 of pollen and honey. 



The fruit of the sunflower has no feathery top or pappus 

 to float it away like the dandelion and thistledown. It is 

 too large and hfavily stored with rich food-stufTs for the 

 young plant to admit of that form of dispersion. So the 

 calyx, instead of being transformed into a pappus, as in 

 most other composites, here remains simple and cuplike. 

 But the seed profits in the end by its richness in oil and 

 other valuable stores, for the sunflower plant is thereby 

 enabled to get that splendid start in life which makes it 

 into one of the tallest and stoutest annuals of temperate 

 climates. Very few species attain so immense a height in 

 a single year. Probably, too, no other annual, except 

 Indian corn, produces so large a number of so richly-stored 

 seeds. It is this provision on the part of the mother plant 

 which allows them to reach so great a stature during a 

 sin^'le short summer. 



