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C 343 



EYS 



1. The acrid or alkaline state of the 

 sap, which has been considered already, 

 when treating of the Canker. 



2. Plethora, or 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. If the 

 extravasation proceeds from this cause, 

 there is but one course of treatment to 

 be pursued root-pruning, and reducing 

 the staple of the soil, by removing some 

 of it, and admixing less fertile earthy 

 components, as sand or chalk. This must 

 be done gradually, for the fibrous roots 

 that are suited for the collection of food 

 from a fertile soil are not at once adapted 

 for the introsusception of that from a 

 less abundant pasturage. Care must be 

 taken not to apply the above remedies 

 before it is clearly ascertained that the 

 cause is not an unnatural contraction of 

 the sap vessels, because, in such case, 

 the treatment might be injurious rather 

 than beneficial. We have always found 

 it arising from an excessive production 

 of sap, if the tree, when afflicted by ex- 

 travasation, produces at the same time 

 super-luxuriant shoots. 



3. Local contraction of the sap ves- 

 sels. If the extravasation arises from 

 this cause, there is usually a swelling of 

 the bark immediately above the place of 

 discharge. In such a case the cultivator's 

 only resource is to reduce cautiously the 

 amount of branches, if the bleeding 

 threatens to be injuriously extensive, 

 otherwise it is of but little consequence, 

 acting, like temporary discharges of blood, 

 as a relief to the system. 



4. The extravasation of the sap from 

 a wound is usually the most exhausting, 

 and as the wound, whether contused or 

 cut, is liable to be a lodgement for water 

 and other foreign bodies opposed to the 

 healing of the injured part, the discharge 

 is often protracted. This is especially 

 the case if the wound be made in the 

 spring, before the leaves are developed, 

 as in performing the winter pruning of 

 the vine later than is proper. In such 

 case, the vine always is weakened, and in 

 some instances it has been destroyed. 



5. Heat attended by dryness of the 

 soil, as during the drought of summer, 

 is very liable to produce an unnatural 

 exudation. This is especially noticeable 

 upon the leaves of some plants, and is 

 popularly known as honey -dew. It is 



somewhat analogous to that outburst. oF 

 blood, which in such seasons is apt to 

 occur to man, and arises from the in- 

 creased action of the secretory and circu- 

 latory system to which it affords relief. 

 There is this great and essential difier- 

 ence, that, in the case of plants, the ex- 

 travasation is upon the surface of the 

 leaves, and in proportion, consequently, to 

 the abundance of the extruded sap are 

 their respiration and digestion impaired. 



Azaleas sometimes, but rarely, have 

 the hairs on their leaves, especially on 

 their lower surface, beaded, as it were, 

 with a resinous exudation. This can 

 scarcely be called a disease. It is never 

 found but upon plants that have been 

 kept in a temperature too high, and in 

 a soil too fertile. It is an effort to relieve 

 the surcharged vessels, and occurs in 

 various forms in other plants. 



The various successful applications of 

 liquids to plants, in order to prevent the 

 occurrence of the honey-dew and similar 

 diseases, would seem to indicate that a 

 morbid state of the sap is the chief 

 cause of the honey-dew, for otherwise it 

 would be difficult to explain the reason 

 why the use of a solution of common 

 salt in water, applied to the soil in which 

 a plant is growing, can prevent a disease 

 caused by insects. But if we admit tht 

 the irregular action of the sap is the 

 cause of the disorder, then we can under- 

 stand that a portion of salt introduced in 

 the juices of the plant would naturally 

 have an influence in correcting any mor- 

 bid tendency, either preventing the too 

 rapid secretion of sap, stimulating it in 

 promoting its regular formation, or pre- 

 serving its fluidity ; and that by such 

 a treatment the honey-dew may be en- 

 tirely prevented, we have often witnessed 

 when experimentalizing with totally 

 different objects. Thus we have seen 

 plants of various kinds, which have been 

 treated with a weak solution of common 

 salt and water, totally escape the honey- 

 dew, where trees of the same kind 

 growing in the same plot of ground not 

 so treated, have been materially injured 

 by its ravages. 



EYE-BKIGHT. Euphra'sia. 



EYSENHA'RBTIA. (Named after Eysen- 

 hardt, a Prussian botanist. Nat. ord., 

 Leguminous Plants [Fabaceffi]. Linn., 

 17 -Diadclphiu &-Decandria. Allied to 

 Amorpha.) 



Cuttings ot young shoots in sand, in bottom- 



