DICTYOSPORIUM. 



[ 208 ] 



DIDYMIUM. 



Fig. 1/5. 



DICTYOSPORIUM, Corda. A genus of 

 Torulacei (Coniomycetous Fungi) containing 

 one species, D. eleyans 

 (fig. 1/6), a minute fun- 

 gus growing upon oak 

 which has been stripped 

 of its bark ; very remark- 

 able for the reticulated 

 character of its spores Dictyosporium ele&ans . 



BIBL, Berk, and Br. Sp y J s magnifie S d 

 Ann. Nat. Hist. 2ser. v. 1000 diameters. 

 p. 460 ; Corda,/cow. Fung. 

 li. pi. 8. fig. 29. 



DICTYOTA, Lamx. A genus of Dictyo- 

 tacese (Fucoid Algae), containing one British 

 species, D. dichotoma, common between 

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

 its dichotomously dividedmembranous 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^E. AfamilyofFucoidese. 

 Olive-coloured inarticulate sea-weeds, with 

 large spores like those of Fucaceae, 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. Frond ribless, dichotomous. 

 Sori roundish, scattered, bursting through 

 the epidermis, or (on distinct individuals) 

 scattered spores. 



For other genera often included here, 

 see SPOROCHNACE^E, PUNCTARIACE^E, 

 DICTYOSIPHONACE.E, and CUTLERIACE^E. 



BIBL. See the genera. 



DICTYOXYPHIUM, Hooker. A genus 

 of Lindsaeese (Polypodaeous Ferns). Exotic. 



DIDERMA, Pers. A genus of Myxo- 

 gastres (Gasteromycetous Fungi), consisting 

 of minute epiphytic plants, of tolerably per- 

 sistent structure (fig. 1/6). -pis 176 

 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 le P idotum - 

 which are found filaments Ma & n - 25 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,lieslooseintheoutercase. 

 The species vary in habit, being either stipitate 

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

 (Leocarpus, Lk.) distinct in different 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; SummdVeg.450; Greville, Sc. 

 Crypt. Fl. pis. 3. 122 & 132 ; Corda,Ic. Fung. 



DIDYMIUM, Schrad. A genus of Myxo- 

 gastres (Gasteromycetous Fungi), consisting 

 of minute plants growing upon leaves, bark, 

 rotten wood, &c. (fig. 177), distinguished by 

 its double peridium, of which, however, the 

 inner membranous layer 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 twiningamong 

 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 

 Didermce, being either stalked, sessile, or 

 adnate to their support. D.farinaceum is 

 figured (pi. 240) by Sowerby as Trichia 

 sphterocephala. 



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. 



Didymium 

 liquidum. 



