DICTYOXYrillUM. 



[ 2G1 ] 



DIDYMOCIIL^NA. 



Sori roundish, containing 



or scattered. TJoot coated with woolly 

 fibres. Frond flat. 



Many other genera are included in this 

 faniily by most authors ; but Thui'et has 

 pointed out that the genera here named 

 produce spoi-es, while the structures de- 

 scribed as such in the others are oospo- 

 ranges. Padixa presents some interesting 

 points of microscopic structm-e. All the 

 genera are formed of very regular muri- 

 form parenchyma. 



British Genera. 



Haliseris, Frond dichotomous, with a 

 midrib. 



Padina. Frond ribless, fan-shaped, con- 

 centrically streaked. Sori linear, concen- 

 tric, bursting through the epidermis. 



Zonaria. Frond ribless, lobed, concen- 

 trically striate 

 spores and jointed threads 



Taonia. Frond ribless, irregularly cleft, 

 some what fan-shaped. Sori linear, concen- 

 tric, superficial, alternating with scattered 

 spores. 



Dicfi/ofa. Frond ribless, dichotomous. 

 Sori roundish, scattered, bursting throug-h 

 the epidermis, or (on distinct individuals) 

 scattered spores. 



For other genera often included here, see 

 Spoj80ch:n-ace.^e,Puxctariace.^,Dictyo- 

 siPHOXACE^, and Cutleriace^e. 



BiBL. See the genera. 



DICTYOXYPH'IUM, Hooker.— A ge- 

 nus of Lindsayeoe (Polypodiaceous Ferns). 

 Exotic. 



DICYE'MA, KolL— A genus of Infuso- 

 ria (?), allied to Opalina. 



D. Miilleri is found in the kidneys &c. of 

 Cephalopoda. 



BiBL. Erdl, Erichs. Arch. 1843, 162; 

 Kolliker, Wllrzhurg Ber. 1849 ; Clap, and 

 Lachm. Infax. ii. 201. 



DIDER'MA, Pers.— A genus of Myxo- 

 mycetes, consisting of minute epiphytic 

 plants of tolerably persistent structure 

 (fig. 173). The peculiar cha- 

 racter resides in the double Fig. 173. 

 layer of the peridium, the 

 outer being smooth and crust- 

 like, fragile and dehiscent, 

 while the inner is very deli- 

 cate and evanescent. The spe- 

 cies vary in habit, being either 

 stipitate with the stalk more dotum. 

 {Leangium, Uk.) or less {Leo- yi^^i^^^2o 

 carpus, Lk.) distinct in dif- diams. 

 ferent cases, and sessile. A 



Diderma lepi- 



dozen species are recorded as British, of 

 whicli the sessile D. g/ohosum, and the ob- 

 scurely stalked D. i-ernicosnm, appear the 

 commonest. 



BiBL. Berk. Hook. Br if. Fl. v. pt. 2. 

 310 ; Ann. N. II. i. 257 ; (Jrgpt. Bot. 337 ; 

 Fries, Syst. Myc. iii. 96 ; Summa Veg. 4o0 ; 

 Greville, So. Cnjpt. Fl. pis. 3, 122 & 132 ; 

 Corda, Ic. Funq. 



DIDIMTUM, Stein.— A genus of Peri- 

 trichous Infusoria. 



Char. Free, ovate, or subcylindrical, with 

 an anterior and posterior ciliary wreath; 

 snout-like in front. 



B. nasutiim. Pond- water ; length 1-300", 

 (Kent, Inf. 638.) 



DIDYM'lUM, Schrad. — A genus of 

 Myxomycetes, consisting of minute plants 

 growing upon leaves, bark, rotten wood, 

 &c. (fig. 174), distinguished by its double 

 peridium, of which, however, the inner 

 membranous layer is the true case 

 (bursting irregularly), while the Fig. 174. 

 outer forms a kind of bark, which 

 breaks up into little furfuraceous 

 scales or mealy down. Filaments 

 exist twining among the spores 

 adherent to the peridium. Six- 

 teen species are recorded as Bri- 

 tish, several of which are not 

 uncommon. They vary in habit, 

 like the Didermce, being either 

 stalked, sessile, or adnate to their 

 support. Z). farinaceum is figtu'ed 

 Sowerby as Trichia sphcerocephula. 



BiBL. Berk. Hooh. Br. Fl. v. pt. 2, 312 ; 

 Ann. N. H. i. 257, 1850, v. 365, xiii. 459 ; 

 Crypt. Botany, 337 ; Fries, Syst. Myc. iii. 

 113 ; Sumtna Vec/. 451 ; Sowerbv, Fungi, 

 pis. 12, 240, 412; Corda, Ic.Fung. 



DIDYMOCHL.E'NA, Desv.— A genus 



Fig. 175. 



Fig. 176. 



Liidjaiiium 



hemispha;- 



rieum. 



Magnified 

 20 diams. 



^J 



Didymoehlfena ainuosa. 

 Fig. 175. A Borus, from above. Magn. 20 diams. 

 Fig. 176. Transverse vertical section of ditto. 



