September, 1903.] 



KNOWLEDGE, 



193 



IlLUSTRATBD MAGAZl 



[ii€EJ.iTERAT!JSrS 



Founded by RICHARD A. PROCTOR. 



Vol. XXVI.] LONDON: SEPTEMBER, 1903. [No. 215. 



CONTENTS. 



Familiar Britisli Wild Flowers and their Allies. V. — 

 Heaths and Gentians. By R. Lxoyd Pbaeoeb. 



{Illustrated) 



Modern Cosmogonies. IV. — Tidal Friction as an Agent 

 in Cosmogony. By AoxEs M. Clekke 



Stellar Satellites. By J. E. Gobe, y.r.k.s. 



Photographs of Comet c 1903 (Borelly). By Isaac 

 Roberts, d.sc, f.b.s. {Plate.) '. 



Cycles of Eclipses. By A. 0. D. Crommelin. {Illustrated) 



Letters : 



The Sureoundinos op the " America " Nebul.\. By 

 Isaac Roberts 



Trotective Resemblance in Butterflies. By W. S. 

 Rouers. Note by Gr. H. Carpenter ... 



CnEiotis SoNSET PuENOMENON. By K. D. Field, lt.b.a. 

 (Illustrated) 



Notes 



Notices of Books 



Books Received 



The Vatican Observatory. Bv W. Alfbhu Parr. 

 {Illustrated) " 



Microscopy. Conducted by M. I. Ceos3 {Illustrated) ... 



Notes on Comets and Meteors. By W. P. Dknnino. 



F.R.A.S. , . ... 



The Face of the Sky for September. By W. Shackleton, 



P.B.A.8 



Chess Column. By C. D. LococK, b.a. 



196 

 199 



201 



202 



206 



206 



206 

 207 

 208 

 210 



210 

 212 



214 

 215 



FAMILIAR BRITISH WILD FLOWERS AND 

 THEIR ALLIES. 



By R. Lloyd Praeoee, b.a. 

 v.— HEATHS AND GENTIANS. 

 H KATHs and Gentians ! Wliat pleasant pictures do tlie 

 nanie.s bring before the mind. Beautiful plants, with 

 i^raceful forms and brilliant flowers. Summer days amid 

 tin? hot bee-iilled heather. Wide brown moors, or alpine 

 Hovver-starri'd pastures. In point of fact, the plants 

 const itutiiit,' these ijniups are, lilce the Saxifrai;es, redolent 

 of the wild open country ; of rock, and sand-dune, and 

 mountain solitude. The fertile plains yield but a scant 

 few of them ; about the murky town we seek in vain a 

 single one. And at this season of the year, when many of 

 us are away in the home of tlu^ Heaths and Gentians, or 

 liave still fresh memories of the mountain breeze, and the 

 fragrance of the Heather, we may appropriately spend a 

 little while in a study of plants which give us so much 

 pleasure. 



The Heath family, f)r Ericaeeic, forms an assemblage of 

 shrubs — or occasionally herbs — which have a wide dis- 

 triljution over the globe. They are generally found in 

 rocky or boggy places in temperate countries, and especially 

 frequent sub-alpine regions. The Cape of Good Hope is the 

 home of an immense number of species of the typical and 

 largest genus of the Order Erica. This genus yields the 

 numerovis lovely Heaths that are found in cultivation, and 

 which must be ranked among the most beautiful plants 

 which our greenhouses can boast. The plants of this 

 Order have, as their most remarkable character, their 

 beauty. Only a few possess medicinal or other properties. 

 In the whole vast genus Erica there is not a single 

 instance of a medicinal species. A few members of aOied 

 genera, including the familiar Ling (Calluna vulgaris), and 

 the Bearberry (Arctostaphylos TJva-iirsi), are astringent. 

 Some of the Rhododendrons and Azaleas are strongly 

 narcotic. The berries of some succulent-fruited species, 

 such as the Cranberry, are used as food, liut the list of 

 economic virtues in the Order is very short. But from 

 the point of view of aesthetics, what a gold mine the 

 Ericacem furnish. Not only the myi-iad many-tinted 

 Heaths, but the glorious Rhododendi-ons and Azaleas 

 belong here ; also the Kalmias, Andromedas, Ledums, and 

 Arbutus. The species, as a whole, show a decided 

 preference for peaty soils, and many of them cannot 

 endure lime, which renders difficult the cultivation of the 

 larger sorts, such as Rhododendrons, in certain districts. 



Leaving the gorgeous Himalayan Rhododendrons and 

 Cape Heaths, we must turn to the British representatives 

 of the Ordei-, which, if modest in comparison with these 

 glorious jjlants, are nevertheless full of beauty and interest. 

 The British Ericaceie, taking the term in a wide sense, 

 may be divided into five tribes : Arhutese, characterized 

 by a succulent superior fruit, and represented by the 

 Strawberry-tree and Bearberry ; Ericeie, including the 

 Heaths and their immediate allies, all small shrubs ; 

 Vaccinieie, with a fleshy inferior fruit, represented by the 

 Whortleberry and its relations ; Pyrolem, containing the 

 beautiful Wintergreen ; and Monotropege, consisting of 

 strange white or brown leafless herbs, of parasitic or 

 saprophytic habits. 



The Strawberry-tree, Arbutus TJnedo, is the largest of the 

 British Ericaceie, forming a small bushy tree which may 

 attain a height of twenty feet. Its evergreen fohage, 

 clusters of winter-borne Lily-of-the- Valley-like flowers, and 

 pretty, rough, scarlet fruit, make it a favourite in shrul)- 

 beries. As a native, it grows only in a small portion of 

 the south-west of Ireland. Around the shores and on the 

 islands of the LTpper Lake of Killarney it may be seen at 

 its liest, contributing very materially to the arlx>real vege- 

 tation of that delightful spot. Abroad, it occurs across 

 the Spanish peninsula, and all along the Mediterr.ineau. 

 The Beai-berries {Arctostaphylos) are small evergreen 

 shrubs, with pretty Arhutus-\\Ve flowers and shining 

 berries. A. alpina^ which has bluish-black berries, is a 

 rare Scottish alpine. A. Vva-itrsi is more widely spivad, 

 and though generally alpine in its distribution, in the 

 west of Ireland it descends in sheets to sea-level. It has 

 far-st retching, trailing, branching stems, pink flowers, and 

 bright red herries. 



We come now to the Ericeie, or true Heaths. Of the 

 six British Geuerii— Andromeda, Calluna, Erica, Azalea 

 (= Loiseleuria), Pliyllodoce (= Bryanthus). and Daheocia 

 {=Borelta), all but the third (Erica) have only a single 

 representative. All are small evergreen shrubs, affecting 

 peaty soils. The Marsh Andromeda (A. Polifolia) is a 

 plant of peat bogs, with the leathery recurved leaves, dark 

 green abtn'e and white btnieath, which so many of the 

 Heath allies possess, and pink urn-shaped blossoms, which 



