THELACTIS. 



[ 640 ] 



THYRSOPTERIS. 



It is thus subdivided : — 



A single 



flagelliforni 



filament. 



Two 



filaments. 



'Body ovoid or f Tegument hard and brittle 1 , 



^ globular . . . . t Tegument membranous 2. 



I Body depressed or/ with a tail-like prolongation . . .j.^,. .i^.^^.j^ 3. 



^foliaceous I without a prolongation '!...".!], 4. 



{Two similar filaments 5. 



One flagelliforni filament, and r Body prismatic or boat-shaped 6. PlcBotia 



one trailing retractile filament L Body ovoid or pip-shaped .... /. Anisonema. 



Several filaments (in w''?!''."^!'^ .'!".*!*. ^^^^^^^^ 8- Oayrrhis. 



Trachelomonas. 



Cryptontonas. 



Phacus (Euglena, pt. E.). 



C^ttmenula. 



Diselmis {Chlamidomonas, E.). 



BiBL. Dujardin, Infus. 323. 



THELACTIS, Mart.— A doubtful genus 

 of Mucorini (Physomycetous Fungi), con- 

 sisting apparently of a Mucor vnth. one or 

 more whorls of barren branches near the 

 lower part of the erect fertile filaments. 



BiBL. Fries, SummaVeg. p. 487- 



THELOTREMA, Ach.— A genus of En- 

 docarpese (Angiocarpous Lichens), contain- 

 ing two British species. 



BiBL. Leighton, Brit. Angioc. Lichens, 

 p. 31. 



THEORUS, Ehr.— A genus of Rotatoria, 

 of the family Hydatinsea. 



Char. Eyes colourless, more than three, 

 cervical, in two groups; foot forked; jaws 

 each with a single tooth. 



T. vernalis (PL 35. fig. 32). Toes small, 

 frontal hook absent. Aquatic; length 1-140 

 to 1-120". 



T. uncinatus. Toes long, frontal (or ra- 

 ther cervical) region wuth hooks. Aquatic ; 

 length 1-240". 



BiBL. Ehrenberg, Infus. 454. 



THOREA, Bory.— A genus of Batra- 

 chospermeae (Confervoid Algae), of which 

 one species (T. ramosissima) occurs in Bri- 

 tain; its fronds are branched filaments, a 

 foot or more long, about as thick as a crow- 

 quill, with a villous surface, of olive-black 



Fig. 745. 



Thorea ramosissima. 



Horizontal section of a filament (halved). The semi- 

 circular denser portion represents the axis, the loose 

 spreading branches, the villi. Magnified 25 diameters. 



colour. The filaments are composed of ra- 

 diating branched cells, closely compacted 



into a kind of solid axis, from which proceed 

 lax, radiating ramuli (forming the villous 

 surface). The spores (or sporangial cells) 

 arise from these ramules (fig. 745). 



BiBL. Klitzing, Phyc. generalis, pi. 16, 

 Sp. Alg. p. 534, Eng. Bot. Supp. No. 2948 ; 

 Hassall, Brit. Fr. Alg. p. 64. 



THUJA, L. — A genus of Coniferae (Gym- 

 nospermous Plants), to which belongs the 

 arbor vitce of gardens. Thuja Occident alis ; 

 T. orientalis is placed by some authors under 

 another genus. Biota. The characters of 

 Coniferous wood, Gymnospermous ovules, 

 &c., may be observed in these plants (see 

 Conifers and Ovule). 



THYRSOPTERIS, Kunze.— A genus of 

 Cyathaeous Ferns, with a curious structm'e 

 of the fertile fronds. Exotic (figs. 746-9). 



Fig. 746. 



Fig. 747. 



Fig. 748. 



Fig. 749. 



ThjTsopteris elegana. 



Fig. 746. A fertile pinna. 



Fig. 747. A pinnule converted into a cup-like sorus. 

 IMagnified 20 diameters. 



Fig. 748. Vertical section of the same, with the spo- 

 ranges removed from the columella. 



Fig. 749. Side view of a sporange. Magn. 100 diams. 



