DICTYOXYPHIUM. 



[ 261 ] 



DIDYMOCHL^ENA, 



or scattered. Root coated with woolly 

 fibres. Frond flat. 



Many other genera are included in this 

 family by most authors ; but Thuret has 

 pointed out that the genera here named 

 produce spores, while the structures de- 

 scribed as such in the others are oospo- 

 ranges. PADINA presents some interesting 

 points of microscopic structure. 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. Sari linear, concen- 

 tric, bursting through the epidermis. 



Zonaria. Frond ribless, lobed, concen- 

 trically striate. Sori roundish, containing 

 spores and jointed threads. 



Taonia. Frond ribless, irregularly cleft, 

 some what fan-shaped. Sori linear, concen- 

 tric, superficial, alternating with scattered 

 spores. 



Dictyota. Frond ribless, dichotomous. 

 Sori roundish, scattered, bursting through 

 the epidermis, or (on distinct individuals) 

 scattered spores. 



For other genera often included here, see 

 SPOROCHNACE^PUNCTARIACE^DICTYO- 

 SIPHOXACE^;, and CUTLERIACE^. 



BIBL. See the genera. 



DICTYOXYPH'IUM, Hooker. A ge- 

 nus of Lindsayeae (Polypodiaceous Ferns). 

 Exotic. 



DIG YE' MA, K611. A genus of Infuso- 

 ria (?), allied to Opalina. 



I). Mulleri is found in the kidneys &c. of 

 Cephalopoda. 



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

 Kolliker, Wiirzburg Ber. 1849 ; Clap, and 

 Lachm. Infm. 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 bein 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 

 (Leangium, Lk.) or less (Leo- Magnified 25 

 carpus, Lk.) distinct in dif- diams. 

 ferent cases, and sessile. A 



dozen species are recorded as British, of 

 which the sessile D. globosum, and the ob- 

 scurely stalked D. vernicosum, appear the 

 commonest. 



BIBL. Berk. Hook. Brit. Fl. v. pt. 2. 

 310 ; Ann. N. H. i. 257 ; Crypt. Bot. 337 ; 

 Fries, Syst. Myc. iii. 96 ; Summa Veg. 450 ; 

 Greville, Sc. Crypt. Fl. pis. 3, 122 & 132 ; 

 Corda, Ic. Fung. 



DIDIM'IUM, Stein. A genus of Peri- 

 trichous Infusoria. 



Char. Free, ovate, or subcylindrical, with 

 an anterior and posterior ciliary wreath; 

 snout-like in front. 



D. nasutum. Pond- water ; length 1-300". 

 (Kent, Inf. 638.) 



DIDYM'IUM, 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- f idy 



,. i * in 1.1 hemisphse- 



tish, several of which are not ricum. 

 uncommon. They vary in habit, Magnified 

 like the Didermce, being either 2 diams. 

 stalked, sessile, or adnate to their 

 support. D. farinaceum is figured by 

 Sowerby as Trichia sphcerocephala. 



BIBL. Berk. Hook. Br. Fl. v. pt. 2. 312 ; 

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

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

 113 ; Summa Veg. 451 ; Sowerby, Fungi. 

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



DIDYMOCHL^E'NA, Desv. A genus 



Fig. 175. 



Didymochlaena sinuosa. 



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

 Fig. 176. Transverse vertical section of ditto. 



