THE FARMERS' REGISTER. 



353 



commsrcial enterprise ; and therefore, in the epe- 

 culalioiis now allocit as to the transler of the pro- 

 duclu ol one |)ari of the earth to another, it is ini- 

 porianl to set at rest or establish the principle upon 

 which this must be eH'ecied. 1 do not stand here 

 in order to delend the principles ol' Liebijj, but 

 shall be triad to listen to the experience which any 

 •gentleman here has lo offer; assuring you, that 

 I have at least as much pleasure in listening to 

 others as in hearing myself. 



ON DESTROYING RATS. 



From the London Farmers' Magazine. 



Sir, — The following is a reply to your corre- 

 epondeni's inquiry as to ihe be.*t mode of destroying 

 rate. Should he find either of these methods suc- 

 ceed, he will oblige by a reply through your 

 paper. 



1st — Corks, cut as thin as sixpences, roasted or 



stewed in grease, and placed in their tracks. 



or — Dried sponge in email pieces, fried or dipped 



in honey, with a little oil ol rhodium. 

 or — Bird-lime, laid in their haunts, will stick to 

 their fur, and cause their departure. 

 If a live rat be caught, and well rubbed or 

 brushed over with tar and train-oil, and 

 afterwards put to escape in the holes of 

 others, they will disappear. 

 Poisoning is a very dangerous and objectionable 

 mode. If any of your chemical readers could sug- 

 gest any very pungent smell, procurable from sub- 

 stances resembling garlic or asafcetida, this might 

 be of great use, as this animal has an extraordi- 

 nary fineness or susceptibility of scent : witness 

 its extreme predilection for oil of rhodium, &c. I 

 consider your correspondent's query a very import 

 ant one, and it is surprising that the attention of 

 farmers and othersconcerned in the removal ofthese 

 vermin, has in this age of discovery been so little 

 drawn to tlie subject ; more particularly so, as 

 the newspapers present so many recent instances 

 of attacks made by these creatures on infants, &c. 

 I really think the matter more deserving of 

 notice than has hitherto been given to it ; and, 

 apologizing lor the present intrusion, I remain, 

 yours very truly, 



A Constant S(jbscriber. 

 Bristol, March 10. 



action of leaves. 



Their nature, structure, veins, epidermis, stomates. — 

 Effect of light. — Disestion or decomposition of 

 carbonic acid. — Insensible perspiration.— Forma- 

 tion of secretions. — Fall of the leaf. — Formation of 

 buds by leaves. 



From Liiidley's Horticulture. 



A leaf is an appendage of the stem of a plant. 



such as scales, hooks, tendrils, &c., and even the 

 floral organs, hereafter to be described, have iho 

 same properly. 



Considered with respect to its anatomical struc- 

 ture, a leaf is an expansion of the bark, consist- 

 iiiil o/" cellular substance, among which are dis- 

 tributed veins. The Ibrnier is an expansion of 

 the rind ; the latter consist of woody matter aris- 

 ing Irom the neighborhood of the pith, and from 

 the liber. As the tissue lijrming veins has a 

 double origin, it is arranged in two layers, united 

 firmly during lile, but separable after death, as 

 may be seen in leaves that have been lying lor 

 some time in water. Of these layers, one is su- 

 perior and arises from the neighborhood of the 

 pith, the other inferior and arises from the liber; 

 the (brmer maintains a connexion between the 

 wood and leal ; the latter establishes a communi- 

 cation vviih the bark. As sap, or ascending fluid, 

 rises through the wood, and principally the albur- 

 num, afterwards descending ^rough the liber, it 

 lollows from what has been stated, that a leaf is 

 an organ of which the upper system of veins is 

 in communication with the ascending, and the 

 lower system with the descending current of eap. 

 A leaf has moreover a gkin, or epidermis, 

 drawn all over it. This epidermis is often sepa- 

 rable, and is composed of an infinite number ot 

 minute cavities, originally filled with fluid, but 

 eventually dry and filled with air. In plants 

 growing naturally in damp or shady places it is 

 very thin ; in others, inhabiting hot, dry, ex- 

 posed siluaiions, it is very hard and thick ; and its 

 texture varies between the two extremes, accord- 

 ing to the nature of the species. The epidermis 

 is pierced by numerous invisible pores, called 

 stomateS; through which the plant breathes and 

 perspires. Sucli stomates are generally largest 

 and most abundant in plants which inhabit damp 

 and shady places, and which are able to procure 

 at all times an abundance of liquid food ; they 

 are fewest and least active under the opposite 

 conditions. It will be obvious, that, in both these 

 cases, the structure of a leaf is adapted to the pe- 

 culiar circumstances under which the plant to 

 which it belongs naturally grows. Now, as this 

 structure is capable of being ascertained by ac- 

 tual inspection with a microtcope, it lollows, as a 

 necessary consequence, that the natural habits 

 of an unknown plant may be judged of with con- 

 siderable certainly by a microscopical examination 

 of the structure of its epidermis. The rule will 

 evidently be, that plants with a thick epidermis, 

 and only a fsw small stomates, will be the inha- 

 bitants of situations where the air is dry and the 

 'supply of liquid lood extremely small; while 

 those with a thin epidermis, and a great number 

 of large stomates, will belong to a climate damp 

 and humid ; and iTitermediaie degrees of struc- 

 ture will indicate intermediate degrees of atmo- 

 spherical and terrestrial conditions. It is how- 

 ever, to be observed, that the relative size of 

 stomates is often a more important mark in inves- 

 tigations of this nature than their num-ber ; 



having one or more leaf-buds in its axil. In those organs being in many plants extremely nu- 

 those cases where no buds are visible in the axil, merous, but small and apparently capable of ac- 

 they are, nevertheless, present, although latent, I tion in a very limited degree ; while in others, 

 and may be brought into developement by favo- 1 where they are much less numerous, they are 

 rable circumstances. As this is a universal proper- large and obviously very active organs. Thus 

 ty ot leaves, to which there is no known excep- | the number of stomates in a square inch of the 

 tion, it follows that all the modifications of leaves, : epidermis of Crinum amabiie is estimated at 

 Vol. IX.— 28 



