BLEOHNE.E. 



[ 99 ] 



BLIGHT. 



margin membranous, forming a little lobe. 

 Ma.iiUce (figs. 1 & 2(j, 22 c) bilobed ; inner 

 lobe (laciuia, fig. 22 cf) dilated and ciliated 

 on the inner margin, acute, curved inwards 

 at the apex so as to form a tooth ; outer 

 lobe (galea, fig. 22 c *) longer, thick, rounded 

 and naked ; maxillaiy palpi (figs. 1 & 2 h) 

 elongated, rough with short hairs, 4-jointed, 

 the last joint somewhat hatchet-shaped. 

 Labium (fig. 2-2 e) elongated, bifid, with 

 two more slender inner lobes ; labial palpi 

 (fig. 2 k) pubescent, 3- jointed, last joint 

 truncated obliquely. Mentum (fig. 2 1) short, 

 convex at the base. Eyes (tig. 1 c) kidney- 

 shaped. 



Thorax semicircular, the base convex; 

 elytra coriaceous, one overlapping the other, 

 and with numerous nen-es. Wings large, 

 folded longitudinally, withnumerousnerves. 

 Females apterous. Abdomen flat, oval, 

 and terminated by two short, conical, com- 

 pressed, jointed appendages in both sexes ; 

 besides which, in the male, there are two 

 slender, external, not-jointed appendages or 

 styles, also an elongated intermediate one. 

 Legs long and compressed ; coxfe elongated 

 and stout ; femora stout with a series of 

 spines beneath; tibiae clothed with very 

 strong movable spines ; tarsi 5-jointed, 

 three basal joints gradually diminishing in 

 length ; claws curved and acute. 



An Amceba and some Bursarina are para- 

 sitic in the intestines of Blatta. 



See Insects. 



BiBL. Westwood, Introd. Sfc; Kirby, 

 Brit. Entom. i. 12. 



_ BLECH'NE^.— A family of Polypo- 

 diaceous Ferns. 



Char. Sori linear or oblong, dorsal, paral- 

 lel with the midrib and edge of the seg- 

 ments, not close to the latter. Involucre of 

 the same shape as the sonis, superior, 

 opening towards the midrib. Gen. : 



Blechnmn. Sori linear, continuous or 

 nearly so, parallel with and contiguous to 

 the midrib. 



Sadleria. Sori in a continuous line close 

 to the midrib on both sides, placed on an 

 elevated receptacle. Indusium narrow, sub- 

 coriaceous, at first wrapped over the sorus, 

 then spreading. 



IVooduardia. Sori sunk in cavities in 

 the frond, in single rows parallel with and 

 contiguous to the midribs of the pinnse and 

 pinnules. Indusium subcoriaceous, closing 

 over the cavity like a lid. 



Doodia. Sori oblong or slightly curved, 

 in one or more rows parallel with and be- 



tween the midribs and the margins of tbo 

 pinnre. Indusium membranous. 



BLECH'NUM, Linn.— A genus of Ferns. 

 BL Spicant, With., is the Hard Fern, also 

 called sometimes Bl. boreale, but properly 

 LoM.VRiA Spicant. 



The species are tolerably numerous, closely 

 resembling each other, and dififused -widely 

 throughout Tropical and South Temperate 

 regions. 



BiBL. Hooker & Baker, Syii. Fil. 183, 



BLEPHAmS'MA, Perty, = Plagio- 



TOMA, pt. 



BLIGHT. — This word is used in common 

 language in an exceedingly loose and unde- 

 fined way, being applied to almost every 

 cause of disease in plants, as well as to the 

 diseases themselves, which are variously ex- 

 plained by agencies of meteorological con- 

 ditions, parasitic plants and insects, opera- 

 ting singly or in combination. Blight is, 

 indeed, * in the air ' in many cases, since a 

 frequent source of disease in vegetation is 

 sudden change of temperatiu-e or hygi-o- 

 scopic condition of the atmosphere, deran- 

 ging the processes of evaporation and respi- 

 ration in the tender, actively developing 

 portions of the foliage or inflorescence of 

 plants. It is also often ' in the air ' in an- 

 other sense, but much less specially than is 

 commonly supposed : the plagues of para- 

 sitic fungi and insects which sometimes 

 cause such devastation, seem undoubtedly 

 to arise immediately from the transport of 

 the microscopic reproductive bodies, spores 

 and the like, through the air ; but the pe- 

 culiar atmospheric condition often obsened 

 as accompanying the sudden irruption of 

 large masses of such * blights,' are only col- 

 laterally connected with the development of 

 these bodies ; the warm overcast weather, 

 almost proverbially designated as the cause 

 or the herald of blights, is merely an index 

 of a condition of the atmosphere especially 

 favourable to the rapid multiplication of the 

 Fungi and lusecta which are seen to increase 

 so rapidly at such times ; and the germs of 

 these must be abeady present, through other 

 causes, for the production of the phenomena 

 rmder such circumstances. 



Only a few of the animal blights need be 

 referred to here, such ds the plant-Uce, the 

 most familiar form of ' blight ' in cultivated 

 plants (see Aphid^) ; the ' pepper-corn ' or 

 ' ear-cockle ' of wheat, Atu/uUhda tritici (see 

 ANGtirLLiTLA) ; the wheat-midge (Ceci- 

 D05IYIA); the vine-pest (Phyxloxeea); the 

 turnip-fly (Haltica); the Phytoptid^; 



h2 



