EFFECT OF THE FEOSTS OF 1908-9 ON VEGETATION. 401 



whereas practically all other Mexican shrubs were either killed or 

 severely damaged wherever the cold was severe and they had no special 

 protection. It is, therefore, clearly worth while to try whether plants 

 from districts which have not yielded many hardy plants so far will 

 stand the cold of our winters. The apparently delicate Helxine 

 Soleirolii from Corsica and Sardinia, which is often grown in stoves, 

 is another instance of a plant native where frosts are rare, which has 

 proved capable of surviving such severe cold as that experienced at 

 Wisley and Oamberley, possibly partly because covered by snow, though 

 it should be noted that the grass thermometer registered zero at Wisley 

 under the snow. 



It is a noticeable fact that, while the habit, general character, and 

 structure of a plant are excellent guides to the cultivator as to its 

 requirements of light and water — the two factors that are probably the 

 most important in determining its distribution over small areas — yet the 

 one condition which is most important in determining the distribution of 

 a plant over wide areas of the earth's surface, viz. temperature, leaves 

 no mark upon the plants — there is nothing whatever in the general 

 appearance and structure of a plant to act as a trustworthy guide as to 

 whether it will be capable of withstanding low temperatures or not. 



The natural affinities of plants form a rather better guide, for there 

 are some families which contain no members capable of withstanding 

 low temperatures ; but here again the indication will serve only in some 

 cases, for there are many instances of families, and even genera, of 

 world-wide distribution, and not a few where the majority of the 

 species are restricted to tropical climates but have some representatives 

 straying into countries where the winter temperature falls very low. 



To acclimatize plants has long been an aim of keen horticulturists. 

 Sir Joseph Banks, P.E.S., in a paper read on December 5, 1805, 

 before our Society,''' said: " Eespectable and useful as every branch of 

 the horticultural art certainly is, no one is more interesting to the 

 ; public, or more likely to prove advantageous to those who may be so 

 I fortunate as to succeed in it, than that of inuring plants, natives of 

 j warm.er climates, to bear without covering the ungenial springs, the 

 ' chilly summers, and the rigorous winters by which, especially for some 

 I years past, we have been perpetually visited." And he proposed the 

 I task of raising shrubs liable to be damaged by frost from seeds produced 

 , in this country, instancing, among others, the Bay, the Laurel, Oranges, 

 1 Myrtles, Laurustinus, Cypress, Phillyrea, Alaternus, and Arbutus. 

 ! There is, so far as we have been able to discover, no record of the 

 I results he obtained by sowing seeds of Laurels and Myrtles, but it is 

 I evident that they are as liable to damage to-day as they were then. 

 The common laurel is as much subject to being cut by frost as when 

 j Master Cole, who introduced it to his garden at Hampstead, before 

 I Parkinson pubUshed his Paradisus Terrestris in 1629, " cast a blanket 

 over the top " of it in frosty weather to protect it ; and so we might say 

 of many others. The common potato is no more hardy after cultivation 

 * Trans. Hort. Soc. of London, i. (1807-12), pp, 21-25. 



