DICTYOSPORIUM. 



[ 208 ] 



DIDYMIUM. 



Fiff. 175. 



DICTYOSPORIUM, Corda.— A genus of 

 Torulacei (Coniomycetous Fungi) containing 

 one species, D. elegans 

 (fig. 1/5), a minute fun- 

 gus growing upon oak 

 which has been stripped 

 of its bark; very remark- 

 able for the reticulated 

 character of its spores. t^. , . , 



-r, T. T ' 1 T-. Dictyosporium elegans. 



BiBL. Berk, and Br. J ■« °, 



A TIT TT- " "• '-'^' Spores magnified 



Ann. Nat. Hist. 2ser. v. lOOO diameters. 



p. 460; Corda, Jco/i. Fung. 

 ii. pi. 8. fig. 29. 



DICTYOTA, Lamx.— A genus of Dictyo- 

 taceaj (Fucoid Algae), containing one British 

 species, D. dichotoma, common between 

 tide-marks, on rocks, &c., remarkable for 

 its dichotomously divided membranous frond, 

 of olive-green colour, 3 to 12" long, which 

 produces spores in two ways (on different 

 individuals), either collected in sori or scat- 

 tered. These spores appear to require fur- 

 ther examination. 



BiBL. Harvey, Brit. Alg. p. 39. pi. 7 A; 

 Phyc. Brit. pi. 103; Greville, Alg. Brit. 

 pi. 10. 



DICTYOTACE^.— AfamilyofFucoideffi. 

 Olive- coloured inarticulate sea- weeds, with 

 large spores like those of Fucaceee, superfi- 

 cial, in definite spots or lines {sori), 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 pro- 

 duce spores, while the structures described 

 as such in the others are sporanges. Padina 

 presents some interesting points of micro- 

 scopic structure. All the genera are formed 

 of very regular muriform parenchyma. 



Synopsis of the British genera. 



I. Haliseris. Frond dichotomous, with a 

 midrib. 



II. Padina. Frond ribless, fan-shaped, 

 concentrically streaked. Sori linear, con- 

 centric, bursting through the epidermis. 



III. Zonaria. Frond ribless, lobed, con- 

 centrically striate. Sori roundish, contain- 

 ing spores and jointed threads. 



IV. Taonia. Frond ribless, irregularly 

 cleft, somewhat fan-shaped. Sori linear, 

 concentric, superficial, alternating with scat- 

 tered spores. 



V. Dictyota. Fronc? ribless, dichotomous. 

 Sori roundish, scattered, bursting through 

 the epidermis, or (on distinct individuals) 

 scattered spores. 



For other genera often included here, 



see SpOROCHNACEiE, PUNCTARIACE^, 

 DlCTYOSIPHONACE^, and CuTLERIACEiE. 



BiBL. See the genera. 



DICTYOXYPHIUM, Hooker.— A genus 

 of Lindsoeeae (Polypodaeous Ferns). Exotic. 



DIDERMA, Pers.— A genus of Myxo- 

 gastres (Gasteromycetous Fungi), consisting 

 of minute epiphytic plants, of tolerably per- 

 sistent structure (fig. 176). -p- lyg 

 The peculiar character re- ^' 



sides in the double layer of 

 the peridium, the outer being 

 smooth and crust-like, fragile 

 and dehiscent, while the in- 

 ner is very delicate and eva- 

 nescent. The spores, among Diderma lepidotum. 

 which are found filaments ^^^s^- ^5 diams. 

 adherent either toward the base or to a colu- 

 mella, are at first compacted together into a 

 ball, which, after the absorption of the inner 

 layeroftheperidium,liesloose in the outer case. 

 The species vary in habit, being either stipitate 

 with the stalk more (Leangium, Lk.) or less 

 {Leocarpus, Lk.) distinct in diff'erent cases, 

 and sessile. A dozen species are recorded as 

 British, of which the sessile D. globosum, 

 and the obscurely stalked D. vernicosum, 

 appear the commonest. 



BiBL. Berk, in Hook. Brit. Flor. v. pt. 2. 

 p. 310; Ann. Nat. Hist. i. 257; Fries, Syst. 

 Myc. iii. 96; SummaiVeg. 450; Greville, Sc. 

 Crypt. FL pis. 3. 122 & 132 ; Corda, Jc. Fung. 



DIDYMIUM, Schrad.— A genus of Myxo- 

 gastres (Gasteromycetous Fungi), consisting 

 of minute plants growing upon leaves, bark, 

 rotten wood, &c. (fig. 177)> distinguished bji" 

 its double peridium, of wdiich, however, the 

 inner membranous laj^er is the true case 

 (bursting irregularly), while 

 the outer forms a kind of 

 bark, which breaks up into 

 little scales or mealy down. 

 Filaments exist twining among 

 the spores adherent to the pe- 

 ridium. Sixteen species are 

 recorded as British, several of 

 which are not uncommon. Magn. 25 diams. 

 They vary in habit, like the 

 Didermoe, being either stalked, sessile, or 

 adnate to their support. D.farinaceum is 

 figured (pi. 240) tjy Sowerby as Trichia 

 sph(srocephala. 



BiBL. Berk. Hook. Br.Fl. v. pt. 2. p.312, 

 Ann. Nat. Hist. i. p. 257. 2 ser. v. p. 365, 

 xiii. p. 459; Fries, Syst. Myc. iii. p. 113; 

 Summa Veg. 451 ; Sowerby, Fungi, pis. 12. 

 240. 412; Corda, Icon. Fung. 



Fig. 177. 



Didymiura 

 liquidum. 



