THELACTIS. 



[ 640 ] 



THYRSOPTERIS. 



It is thus subdivided : 



A single f Bod y ovoid or f Tegument hard and brittle 1 . Trachelomonas. 



fH pirf < globular I Tegument membranous 2. Cryptomonas. 



filament 1 Bodv de P ressed or / with a tail-like prolongation 3. Phacus (Euglena, pt. E.). 



Lfoliaceous I without a prolongation 4. Crumenula. 



Two f ^ wo 8 i m ^ ar filaments 5. Diselmis (Chlamidomonas, E.). 



fila t I < " >ne fi a S e ^ orm filament, and /Body prismatic or boat-shaped 6. Pleeotia. 



tone trailing retractile filament I Body ovoid or pip-shaped 7. Anisonema. 



Several filaments 



/rrhis. 



BIBL. Dujardin, In/us. 323. 



THELACTIS, Mart. A doubtful genus 

 of Mucorini (Physomycetous Fungi), con- 

 sisting apparently of a Mucor with one or 

 more whorls of barren branches near the 

 lower part of the erect fertile Hlaments. 



BIBL. Fries, Summa Veg. 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 Hydatinaea. 



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 with 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. Kiitzing, Phyc. generalis, pi. 16, 

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

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



THUJA, L. A genus of Conifers (Gym- 

 nospermous Plants), to which belongs the 

 arbor mice of gardens, Thuja occidentalism 

 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, Kuiize. A genus of 

 Cyathaeous Ferns, with a curious structure 

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



.folido s }o bmslg fc/o-r^riJ 3nJ moil >-r>PT'??/ \ 



Fig. 746. Fig. 747. 



Fig. 748. 



Thyrsopteris elegan 



Fig. 746. A fertile pinna. 



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

 Magnified 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. 



