EVE 



216 



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EVENING PRIMROSE. CEnotkera. 1 summer, when the moisture supplied to 



EVERGREENS are such plants as do I a club-rooted cabbage by its root does 



not shed all their leaves at any one ; not nearly equal the exhalation of its 



season of the year. I foliage, to supply this deficiency the 



EVERGREEN THORN. Cratagusl plant endeavours', by forming a kind of 



pyracantha. 



EVERLASTING. Gmiphalium. 



EVERLASTING PEA. Lathyrus 

 latifolivs. 



EVODIA triphylla. Stove evergreen 

 shrub. Cuttings. Sandy loam. 



spurious bulbous root, to adapt itself to 

 the contingency." — Princ. of Garden- 

 ing. 



EXTRAVASATED SAP. "Under 

 this general name, I purpose to include 

 the consideration of gumming, bleeding, 



EVOLVULUS. Eleven species, and other injurious affections under 



Chiefly stove annual trailers; two are 

 hardy, and tvifo evergreens. The last 

 propagated by division ; others by seed. 

 Common soil. 



EXCRESCENCE. «' Independent of 

 Galls, which are caused by the punc- 

 tures of insects, and the swellings which 

 always a<;company Canker, the excres- 

 cences which injure the gardener's 

 crops are very few. That which ap- 

 pears above the point of union between 

 the scion and stock, is caused by the 

 former being the freer grower of the 

 two, and is a warning which should be 

 remembered, for it curtails the longevity 

 of the tree, the supply of sap gradually 

 becoming inefficient. 



"The excrescences which occur upon 

 the branches of some apples, as those 

 of the codling and June-eating, cannot 

 be looked upon as disease, for they 

 arise from congeries of abortive buds, 

 which readily protrude roots if buried 

 in the soil, making those among the 

 very few apples which can be propa- 

 gated by cuttings. Of a similar nature 



which plants occasionally labour, on 

 account of their sap escaping from the 

 properly containing vessels. The ex- 

 travasation proceeds either from the al- 

 burnum or from the inner bark and may 

 arise from five causes. 



" 1. The acrid or alkaline state of 

 the sap, which has been considered 

 already, when treating of the canker. 



" 2. From plethora or excessive 

 abundance of the sap. 



" 3. From the unnatural contraction 

 of the circulatory vessels. 



" 4. From wounds. 



"5. Heat and dryness. 



" 1. With regard to the alkaline state 

 of the sap, it may be observed, addition- 

 ally, that the excessive alkaline quality 

 of the sap, imparting to it the power of 

 destroying the fibre of its containing 

 vessels, is placed on the basis of chemi- 

 cal experiment. A weak alkaline solu- 

 tion dissolves woody fibre without 

 alteration; and it may be thrown down 

 again by means of an acid. By this 

 property we are enabled to separate 



are the huge excrescences so prevalent j wood from most of the other vegetable 

 on aged oaks and elms. Bulbous ex- 1 principles, as few of them are soluble 



crescences are formed upon the roots of 

 many plants if compelled to grow upon 

 a soil drier than that which best suits 

 them. This is the case especially with 

 two grasses, Phleum pratense and Al- 

 opecurus gcniculatiis, and is evidently a 

 wise provision of nature to secure the 

 propagation of the species, for those 

 bulbs will vegetate long after the re- 

 mainder of the plant has been destroyed 

 by the excessive dryness of the soil. 



"On the free performance of this 

 function of plants their health is depend- 

 ent in a very high degree : and I believe 

 that half the epidemics to which they 

 are subject arises from its derangement. 

 That consequence of the clubbing of 

 the roots of the brassica tribe, called 

 fingers and toes, arises, I consider, 

 entirely from it. In the drought of 



in weak alkaline leys. 



" It is true, that the vital principle 

 may counteract powerfully this chemi- 

 cal action ; but it will not control the 

 corrosive effect of an active agent in 

 excess, if repeated for any length of 

 time. The blood of the human system 

 contains, when in a healthy state, a por- 

 tion of common salt; yet, if this saline 

 constituent is in excess, it induces in- 

 flammation and organic derangement. 



" 2. Plethora is that state of a plant's 

 excessive vigour in which the sap is 

 formed more rapidly than the circulatory 

 vessels can convey it away. When this 

 occurs, rupture must take place, for the 

 force with which it is propelled during 

 circulation, and consequently, the force 

 acting to burst the vessels during any 

 check, is very much greater than could 



