OCTOHER, 1901.] 



KNOWLEDGE. 



217 



MiffiCLilTERATURE A^V 



Founded by RICHARD A, PROCTOR. 



Vol. XXIV.] LONDON: OCToUER, 1901. [No. 192. 

 CONTE N TSi 



• PAOK 



Flowering Plants, as Illustrated by British Wild- 

 Flowers. — V. Dispersal and Distribution. iiy 

 K. Li.OTn Phakqer, B..\. (Illustrated) ... 217 



The White Nile — From Khartoum to Kawa. — IV. 

 Camping and Collecting. J!v Harry F. Witiierby, 

 F.Z.S.. M.li.o.r. (IllustrateilJ ... 220 



Plant-bearing Hair. Hy R. Ltdekkeb 22;i 



The Total Solar Eclipse of May 18, 1901. By E. Walter 



MArXDEB, F.R.A.s. (Illustrated) ... ... ... 225 



The Corona of 1901, May 18. (Piute.) 



Constellation Studies. — IX. The Sea-Monster and 

 the Flood. By E. A\'alter Maukdeb, f.r.a.s. 

 fllluslrafeitj .. . 



Obituary :— Prop. Baron von Nordbnskjold 



Letters : 



Thk DlSTRIBrTIOX OP THE SlAES IX SPACR By .ARTHUR 



Ed. Mitchell. Note by the Eds 



SlTDDBN Blancuixo OP HuMAJf Haib. By Sir W. R. 

 GOWBRS. Sr.D., F.R.S. 



A Triplb Raisbow. By G. McKenzie Knight 

 MOTUING IX SrPFOLK. By Jo3. F. Green 

 SuNSPOTS AND LiGHT. By A. Elvins. Note by E. W. 

 Mauhdee ... 



Notices of Books 



Books Received 



British Ornithological Notes. 



WiTHBBBT, F.Z.S., M.B.o.r. ... 



Notes 



The Mechanism of a Sunset. 

 Microscopy. Conducted by JI. I. 

 Notes on Comets and Meteors. 



F.B.A.S 



The Face of the Sky for October. By A. Fowleb, 



F.B.A.S. ... 



Chess Column. 



Conducted by Habbt F. 



By Aethue H. Beli. 

 Cboss. (Illustrated) 



By W. F. Denning, 



Sky 

 By C. D. LococE, b.a. 



228 

 230 



231 



231 

 231 



2:!l 



232 

 232 

 233 



233 

 234 

 235 

 237 



238 



230 

 240 



FLOWERING PLANTS, 



AS ILLUSTRATED BY BRITISH WILD-FLOWERS. 



By R. Lloyd Praeger, b.a. 

 v.— DISPERSAL AND DISTRIBUTION. 

 To resume the consideration of the means employed by 

 plants to ensure a wide dispersal of their seeds. We have 

 seen how much the available motive agents — wind, 

 water, animals — are taken axlvantage of. There is, in 

 addition, a large number of plants which do not rely on 

 any external agency to cany their seed, but do the 

 scattering themselves, by one or another ingenious 

 device. If we lie on a sunny bank among the Gorso in 

 August, we shall hear a sharp snapping noise coming 

 from the prickly bushes at frequent intervals. This is 

 due to the sudden rupturing of the ripe pods, owing to 

 unequal- shrinkage caused by their drying. The walls 

 of the fruit are composed of layers of colls which vary 

 in the amount to which drying causes them to contract. 

 When the stress due to the irregular contraction thus 

 produced reaches a certain point, the walls give way. 



and each half of tho pod jerks into a spiral form, 

 projecting the endoscil seeds to a considerable distance. 

 Examine a fruit of tho common Dog Violet. It is 

 a little capsule formed of three sections. As it ripens 

 it opens along the lines of junction of these, and wo 

 get three narrow boat^shapcd valves spreading horizon- 

 tally from tho fruit-stom, and each containing sevoral 

 seeds. The drying of these valves causes contraction. 

 Tho two gunwales, so to speak, of each boat are drawn 

 together, "pressing more and more tightly on tho seeds 

 which lie between, till one by one the seeds spring out 

 with considerable force. 



In other cases a similar violent expulsion of the seeds 

 is caused by unequal growth in the tissues of the seed- 

 vessel. This it is that produces such a stato of stress in 

 tho five-parted capsules of the Touch-me-not that when 

 ripe a puff of wind or a light touch causes a violent 

 explosion of the fruit, by which the seeds arc scattered 

 far and wide. A moro familiar example may be studied 

 in the little Haiiy Cress, so common a weed in gardens. 

 While weeding a lx;d early last June, in which there 

 was a quantity of this plant, which had unwisely been 

 allowed to excewl tho period of flowering, the bursting 

 of the little narrow pods and the flinging of hundreds 

 of seeds in my face amounted to a positive nuisance, 

 and caused reflections concerning the wisdom of an old 

 saying about a stitch in time. 



Some of tho Crane'srbills fling their seeds to a con- 

 siderable distance by means of a moro complicated 

 apparatus. The fruit consists of five separate caijicls 

 attached by their apices to a spindle. Each carpel con- 

 sist^s of an egg-shaped pouch containing one seed, pro^ 



Fio. 1.— Tlie I'.Ioody Craut-'j-bill, sliowiiig slins-fruit. I nat. size, 



longed into a slender rod, the whole adprcsscd to the 

 spindle, so that the five pouches lie in a ring round its 

 base. Each pouch is open on the side which is pressed 

 against the spindle. As the fruit ripens, the more rapid 

 shrinking of the outer layers of the rod of the carjiel 

 causes it to rupture the tissue which attaches it by its 

 whole length to the spindle, and it curls with a jerk, 

 cariying up the pouch, and causing the seed to fly out 



