^ECIDIUM. 



AERIAL ROOTS. 



which is ultimately only recognizable where 

 it connects the spores together in a monili- 

 forin series. The spores in most cases now 

 acquire a deeper colour (except in &. leuco- 



jEcidium Compositarum, Mart. 

 Fig. 6. 



Peridia in various stages of growth on the surface of a 

 leaf: 30 diam. 



Fig. 6rt. 



Perpendicular section through a burst peridium, show- 

 ing the sporanges contained in it : 100 diam. 



coniwri). owing to contents chiefly accu- 

 mulated in the centre. Their membrane 

 is colourless, their form finally irregularly 

 polygonal ; and the diameter varies much, 

 even in ripe spores of one and the same 

 species, from 1-1000 to 1-1800 of an inch. 

 The upper spores are often ripe at an epoch 

 when young spores are still in course of pro- 

 duction at the lower end of the sporanges j 

 finally, however, the development ceases be- 

 low, and the tube elongates a little beneath 

 the lowest spore, forming a kind of pedicle 

 or basidium to the row. The ripe spores 

 either soon fall apart and fill the cup as a 

 loose powder, along with short incomplete 

 sporanges, or the rows persist even after 

 they are mature, held together probably by 

 a firmer peridial membrane. 



The British species of dEcidium are nu- 

 merous; more than thirty are described by 

 Berkeley in the British Flora, many of 

 which are common, especially those of the 

 Mints, the Composites (such as the Colts- 

 foot, &c.), the Barberry, the Gooseberry, 

 Buckthorn, Spurge, Nettle, &c. (&. Com- 

 positarum, Mentlice, Berberidis, Grossularice, 

 crassum, Euphorbia. Urticcs, ifci). 



Oersted and De Bary have made expe- 

 riments which seem to prove that JEcidium 

 Berberidis is a development of Puccinia 

 graminis', a full account of which will 

 be found in Cooke and Berkeley, Fungi. 

 p. 180. 



BIBL. For Species : Brit. Flora, ii. pt. 2. 

 p. 369 j Greville, Sc. Crypt. Flora, pis. 7, 

 62, 97, 180, 209 ; Reess, Disp. Ured. 1879. 



For Anat. and Physiol. : Unger, Exan- 

 theme, pp. 297, 300," t. 3. f. 18, 19, t. 4 ; 

 Meyen, Pftanzenpath. pp. 143, 148-50 ; 

 Tulasne, Compt. Rendus, March 24 and 31, 

 1851 j Ann. d. Sc. Nat. ser. 3. t. xv. ; ibid. 

 ser. 3. t. vii. p. 45 ; ser. 4. t. ii. pp. 12(3, 173 ; 

 Leveille, Sur le dev. des Uredinees, Ann. 

 des Sc. Nat. ser. 2. t. xi. ; Corda, Icon. Fung. 

 iii. t. 3. f. 45 j De Bary, Brandpilze, Berlin, 

 1853, p. 55 et seq. pis. 5, 6, and 7 ; Sachs, 

 Botanik, 1874, p. 332 j Henfrey, Bot. (Mas- 

 ters), 1878, p. 460. 



^GERITA, Persoon. A. genus of Stil- 

 bacei (Hyphomycetous Fungi) characterized 

 by short necklace-like threads consisting of 

 irregular spores produced from flexuous, 

 branched, radiating sporophores, forming a 

 subglobose mass. JE. Candida, Persoon, 

 grows on damp twigs in marshy places, 

 consisting of scattered white grains about 

 the size of a poppy-seed. AZ. setosa, Grev., 

 belongs to the genus Volutella. 



BIBL. Greville, Crypt. Fl. pi. 268. n>. 1 ; 

 Ann. N. II. 1859, iii. 362, pi. ix. f. 7. 



./EGYRIA. A genus of Infusoria =Zr- 

 vilia, Duj. A. legumen=E)-v. legumen, D. 

 Three other species. 



BIBL. Claparede and Lachmann, Infus. 

 $c. i. p. 288. 



ANGSTROE'MIA, Br. and Sch. A ge- 

 nus of Leptotrichaceous Mosses, including 

 many Dicrana, and Ceratodon cylindriciis, 

 Br. and Sch. 



BIBL. Miiller, Synops. Muse. i. p. 426 : 

 Wilson, Bryolog. Brit. pp. 72, 85. 



AERIAL ROOTS. A very large pro- 

 portion of the exotic Orchids are epiphytic 

 plants and produce aerial roots, which "ab- 

 sorb moisture from the atmosphere; the 

 same structure occurs in many tropical 



c'2 



