PARASITES. 



[ 579 ] 



PARMELIA. 



which is the Muscardine of the Silk-worm, 

 BOTRYTIS bassiana, which sometimes occa- 

 sions enormous loss to the silk-cultivators. 

 This fungus grows in or upon any part of 

 the silk- worm, Bombyx mori, in its larva, 

 chrysalis, and imago forms. It is not fully 

 developed until after the death of the insect ; 

 but if the spores penetrate the body of a 

 living specimen and this is placed in a damp 

 and confined atmosphere, the germination 

 takes place, and a development of the fungus 

 ensues, which destroys the tissues and organs, 

 finally causing death. It has been developed 

 on many other Lepidoptera which have 

 been inoculated with it ; and even the larvae 

 of certain Coleoptera take it. It is very 

 common to find flies in autumn infested 

 with a fungus, a kind of muscardine of flies : 

 this belongs to the genus SPORENDONEMA ; 

 its mycelial filaments ramify in the interior 

 of the body, and emerge at the articulations 

 of the segments of the abdomen to bear fruit, 

 killing the fly. A number of so-called genera 

 of Fungi and Algae have been described by 

 Robin and Leidy as occurring in the intes- 

 tines &c. of insects : these appear to us to 

 be imperfect organisms (see ENTEROBRYUS, 

 ARTHROMITUS, LEPTOTHRIX, CLADOPHY- 

 TUM). Several species of Cwrdyceps infest 

 the larvae of insects, the mycelium destroy- 

 ing them and gradually completely dis- 

 placing the internal organs, while the skin 

 retains its shape and dries ; the fruit sub- 

 sequently breaks out from the anterior or 

 posterior extremity (see SPH^RIA). Some 

 species of ISARIA, described as parasites, 

 grow upon dead insects ; but these are mere 

 conditions of different species of Cordyceps. 



The microscopic vegetable parasites of 



Plants 



are very numerous, all belonging to the class 

 of Fungi. Much confusion "exists in many 

 works between the true parasites and mere 

 epiphytes ; and it is sometimes very difficult 

 to draw any line of demarcation. Among 

 the undoubted parasites are all the genera 

 and species of the familyUREDiNEi, together 

 with a large portion of the other genera of 

 Couioinycetes and the Asconiycetous forms 

 to which they mostly belong. Among the 

 Hyphomycetes may^especially be cited the 

 genus PEROXOSPORA, P. infestans being the 

 potato-fungus. FUSISPORIUM, OJDIUM, &c. 

 form destructive mildews ; and among the j 

 ASCOMYCETES, the ERYSiPH^J, and espe- i 

 cially their inycelia (commonly forming | 

 spurious Oidia), are well-known pests, j 



Further particulars are gi ven under POTATO - 

 FUNGUS (Botrytis m/afon0),Yntx-Ft7N<}u8, 

 and BLIGHT. The organisms described as 

 Unicellular Algae, under the names of 

 CHYTRIDIUM and Pythium, are parasitic 

 on Confervoids. 



BIBL. Robin, Veget. Parasit. ; Baeren- 

 sprung, Ann. N. H. xii. ; Siebold, Wagner's 

 Hand. d. Phys. ; Hannover, Mutter's Arch. 

 1842 ; Bennett, Ed. Phil. Tr. xv. ; Archer, 

 Qu. Mic. Jn. 1872, 366 ; Cobbold, Parasites ; 

 Leuckart, Mensch. Parasit. 1881 ; Murie, 

 Mn. M. Jn. vii. 149 ; Maddox, Mic. Tr. 1866 ; 

 Beneden, Schmarotzer,1876 -, Hallier, Phijto- 

 pathol. 1868; Kaltenbach, Pftanzenfeinde 

 (Insects)) 1872; Giebel, JSpvtoa (Insects) , 

 1874; Douiion, Par. diar. Cochin- China; 

 Gurlt,Arch. Naturgesch. 1878, 162 ; Hartig, 

 PftanzenKr. (Fangi), 1880; Frank, Krankh. 

 Pft. (Fungi), 1880; Heller, Schmarotzer, 

 1880 ; Megnin, Paras. 1880 ; Ornierod, In- 

 jurious Insects, 1881 ; Cohn, Paras. Algce 

 Beitrage, i. 87 ; Kiichemneister, Parasiten, 

 1881 ; Bollinger, Pilzkrankh. nied. und 

 Jwh. Thiere, Bot. Centralblatt, ii. 274 (Jn. 

 Mic. Soc. 1881, 492) ; Hallier, Zeitschr. 

 Paras. Kunde. 



PAREN'CHYMA. See TISSUES, Vege- 

 table. 



PARKE'RIA, Carpenter. A large 

 spheroidal Arenaceous Foraininifer, attain- 

 ing 3 inches and more in diameter, and 

 consisting of a chambered conical centre- 

 piece (primordial chamber-cone) surrounded 

 by numerous concentric lamellae and their 

 interspaces, traversed and connected by 

 radial tubes, all of cancellated (labyrinthic) 

 structure. Fossil in the Greensand. 



BIBL. Carpenter, Phil. Trans. 1869, 721. 



PARKE'RIA, Hooker, = CERATO- 



PTERIS. 



PARME'LIA,Ach. An extensive genus 

 of Parmeliaceae, characterized by the spread- 

 ing, lobed, foliaceous thallus, with orbi- 

 cular apothecia fixed by a central point 

 beneath ; spores simple ; growing upon 

 trees, palings, rocks, stones, walls, &c. 

 The species with bilocular spores form the 

 genus Physcia. P. parietina, the yellow 

 wall-lichen, is one of the commonest plants 

 of this family, and furnishes a ready means 

 of observing the structure both of the 

 apothecia and the spermogonia (PI. 37. 

 figs. 1-3). 



BIBL. Hook. Br. Fl. ii. pt. 1. 202 ; Engl 

 Bot. pi. 194 ; Sehaerer, Enum. Lich. Europ. ; 

 Tulasne, Ann. Sc. Nat. 3. xvii. 66, 137 ; 

 Leighton, Lich. Flora, 114. 



