EXOGENS 



349 



FAGARA 



E'XOGENS. A name formerly employed for Dicoty- 

 ledons. 



EXOGO NIUM FILIFO'RME. See IPOMCEA FILIFORMIS. 

 EXOGO NIUM PU'RGA. See IPOMCEA PURGA. 

 EXOGO NIUM REPA'NDUM. See IPOMCEA REPANDA. 



EXORRHI'ZA. (From exo, out of, and rhiza, a root ; 

 the roots grow largely out of the soil. Nat. ord. Pal- 

 maceae.) 



An ornamental stove Palm. For cultivation, see PALMS. 

 E. wendlandia'na (Wendlandian). 60. Leaves pinnate. 

 Fiji. 1901. 



EXOSTE MMA. (From exo, externally, and stemma, a 

 crown ; referring to the flower-heads. Nat. ord. Cin- 

 chonads [Rubiaceas]. Linn. s-Pentandria, i-Monogynia. 

 Allied to Luculia.) 



Stove evergreen tree. Cuttings of ripe young shoots 

 in sand, under a glass, in bottom-heat ; loam and peat. 

 Summer temp., 60 to 80 ; winter, 50 to 55. 

 E. longiflo'rum (long-flowered). 30. White. June. St. 



Domingo. 1820. 

 subcorda'tum (nearly heart-shaped). 2 to 10. White, 



fragrant. W. Ind. 1909. 



EXOTICS. Plants belonging to a country different 

 from that in which they are growing. 



EXTRAVASATED SAP 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. Plethora, or that state of a plant's excessive vigour 

 in which the sap is formed more rapidly than the circu- 

 latory 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 extravasation, produces at the same 

 time super-luxuriant shoots. Severe pruning, lopping, or 

 pollarding produces similar results. 



3. Local contraction of the sap vessels. If the ex- 

 travasation 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 con- 

 tused or cut, is liable to be a lodgment 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 . During hot and dry periods in summer, the leaves of 

 certain trees, but more especially Limes and Sycamores, 

 appear covered with a viscid secretion, known as honey- 

 dew. This is caused by enormous numbers of their own 

 particular species of aphis, on the underside of the leaves. 

 The extravasated sap, in this instance, is a liquid ex- 

 creted by the aphides themselves, through or by means of 

 two tubular glands or excretory organs at the tail-end 

 of the insect. The excreted liquid falls on the leaves 

 beneath them, keeping the same in a moist and viscid 

 or sticky condition all day, notwithstanding the heat 

 of the sun. In the case of trees overhanging the side 

 pavement of streets, the stones are kept moist all day 

 through the same cause. Clean water or soap-suds 

 applied to the underside of the leaves by means of the 



garden engine would wash down or destroy the aphides, 

 and thus effect a cure. 



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 that the 

 irregular action of the sap is the cause of the disorder, 

 then we can understand that a portion of salt introduced 

 in the juices of the plant would naturally have an influence 

 in correcting any morbid tendency ; and that by such a 

 treatment the honey-dew may be entirely prevented, we 

 have often witnessed when experimentalising 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-BRIGHT. Euphra'sia. 



EYSENHA'RDTIA. (Named after Eysenhardt, a 

 Prussian botanist. Nat. ord. Leguminous Plants 

 [Leguminosae]. T.inn. ij-Diadelphia, 4-Decandria. Allied 

 to Amorpha.) 



Cuttings of young shoots in sand, in bottom-heat, in 

 April or May ; loam and peat. Summer temp., 60 to 

 85 ; winter, 50 to 55. 



E. amorphoi'des (Amorpha-like). 15. Pale yellow. June. 

 Mexico. 1838. 



FA BA. Garden Bean. (From phago, to eat. Nat 

 ord. Leguminous Plants [Leguminosae]. Linn. ij-Di 

 delphia, 4-Decandria. Now referred to Vicia.) 



For culture, see BEAN. 

 F. vulga'ris (common). See VICIA FABA. 

 equi'na (horse). See VICIA FABA EQUINA. 



FABA'GO. See ZYGOPHY'LLUM. 



FABIA NA. (Named after F. Fabiano, a Spaniard. 

 Nat. ord. Nightshades [Solanaceae]. Linn. s-Pentandria, 

 i-Monogynia. Allied to Vestia.) 



A half-hardy evergreen shrub, having the aspect of a 

 Cape Heath. Seeds in a hotbed, in March ; cuttings of 

 firm young shoots in sand, under a bell-glass, in April ; 

 set at first in a cold greenhouse or pit, and then plunged in 

 a mild bottom-heat ; sandy peat. Winter temp., 40 

 to 48. 

 F. imbrica'ta (scaly). 3. White. May. Chili. 1838. 



FABRI'CIA. (Named after Fabricius, a Swedish 

 naturalist. Nat. ord. Myrtleblooms [MyrtaceaV]. Linn. 

 j.2-Icosandria, i-Monogynia. See LEPTOSPERMUM.) 

 F. Iczviga'ta (smooth-leaved). See LEPTOSPERMUM L^EVI- 



GATUM. 



myrtifo'lia (myrtle-leaved). See LEPTOSPERMUM 



PUBESCENS. 



seri'cea (silky). See LEPTOSPERMUM PUBESCENS. 

 ,, strfcta (erect). See AGONIS MARGINATA. 



FADYE'NIA. (Named after Dr. Fadyen, author of a 

 Flora of Jamaica. Nat. ord. Ferns [Filices]. Linn. 24- 

 Cryptogamia, i-Filices. Allied to Aspidium.) 



This must not be confounded with Endlicher's 

 Fadye'nia, which belongs to Garryads. Stove Fern. 

 Division ; loam and peat. See FERNS. 

 F. proli'fera (proliferous). J. Brown. May Jamaica. 

 1843. 



PAGA'RA. See ZANTHOXYLUM. 



