HOLOTHYRUS. 



[ 325 ] 



HORMOSPORA. 



Char. Body covered with vibratile cilia, 

 oblong-ovate, cylindrical or globular, rounded 

 or truncate in front; no lips nor teeth. 



Cilia arranged in longitudinal rows. 



Ehrenberg admits five aquatic species ; to 

 these Dujardin, who places this genus in the 

 family Paramecia, adds one marine. 



H. ovum, E. (PL 24. fig. 22). Body ovate, 

 subcylindrical, ends subtruncate; internal 

 substance green; length 1-576 to 1-216". 



H. brnnnea, D. (PL 24. fig. 21). Body 

 brown, cylindrical, becoming globular when 

 distended with food and then changing in 

 colour; length 1-120''. 



The encysting process has been observed 

 in two of the species. 



BIBL. Ehrenberg, In/us, p. 314; Dujardin, 

 Infus. p. 493 ; Cohn, Siebold and Kolliker's 

 Zeitschr. iv. ; Stein, Infus. 



HOLOTHYRUS, Gerv. A genus of 

 Araclmida, of the order Acarina and family 

 Gamasea. 



H. cocdnella is nearly as large as a lady- 

 bird (Coccinella], and is found in the Isle of 

 France. 



BIBL. Gervais, Walckenaer's Apteres, 

 iii. 



HOMCEOCLADIA, Ag. A genus of Dia- 

 tomaceae. 



Char. Frustules linear, elongate, arranged 

 in tufts within gelatinous tubes, which form 

 a filiform branched frond. Marine. 



The nature of the markings upon the 

 valves is doubtful. Kiitzing admits the ex- 

 istence of median and terminal apertures 

 (nodules), and places the genus in the same 

 family as Navicula, &c. ; but these are not 

 represented in his figures ; neither are they 

 mentioned bv Ralfs. 



H. Martiana, Ktz. (H. anglica, Ralfs) (PL 

 14. fig. 15; a, portion of frond; b, part of 

 a filament containing two frustules ; c, front 

 view of single frustules, with endochrome ; 

 d, side view of empty frustule). Filaments 

 tufted, polychotomous, setaceous, terminal 

 branches corymboso-fastigiate, acute ; fasci- 

 cles of frustules closely approximated ; frus- 

 tules very long, narrowly linear, obtuse, 

 transversely striated ; length 1-96 to 1-90" ; 

 entire plant 1 to 2" high. 



H. anglica, Ktz. Filaments tufted, seta- 

 ceous, di-trichotomous, branches equal and 

 acute at the apex, fascicles of frustules 

 closely approximated ; frustules very long, 

 exactly linear, obtuse, transversely striated ; 

 length 1-84"; entire plant 1" high. 



Six other species. 



BIBL. Kiitzing, Bacillar. p. 110, and Sp. 



Alg. 97; Ralfs, Ann. Nat. Hist. 1845, xvi. 

 109. 



HOOF. The hoofs of animals consist of 

 the same structure as horn. 



HOOKERIA, Smith. AgenusofHypnoid 

 Mosses. Brit, species : 



1. Hookeria late-virens, Hook, and Tayl. 



2. Hookeria lucens, Sm. 



HOP. The hop plant (Humulus Lsupulus) 

 is remarkable for the glands containing the 

 resinous secretion imparting the aromatic 

 odour. These occur upon the lower face of 

 the leaf, upon the calyx, and, above all, on 

 the scales of the fruit and the seed-coat. 

 They have been examined by Meyen and 

 others, most recently by Personne. They 

 are little stalked cups (PL- 21. fig. 14) com- 

 posed of a single layer of cellular tissue, 

 concave above at first, but as the secretion 

 increases in quantity, the cuticle becomes 

 detached in a plate from the upper surface, 

 except at the rim of the cup, and is pushed 

 up so as finally to form a convex papilla on 

 the top, like the nut projecting from an 

 acorn-cup. The secretion appears to be 

 formed in the cells, and poured out beneath 

 the cuticular pellicle, which is marked with 

 lines corresponding to the side-walls of the 

 cells. Solution of potash and alcohol clean 

 away the resinous secretion and render the 

 structure clear. When the fresh glands are 

 placed in water, they swell and finally burst, 

 the cuticular lid usually separating by a cir- 

 cumscissile dehiscence. 



The hop is subject to a peculiar mildew, a 

 minute fungus, for which see ERYSIPHE 

 (Spharotheca}. 



BIBL. Meyen, Secretions - Or gane der 

 Pflanzen, p. 38. pi. 5. figs. 17-21; Personne, 

 Ann. des Sc. nat. 4 ser. i. p. 299. pi. 17. 



HOPLOPHORA, Koch. A genus of 

 Arachnida, of the order Acarina and family 

 Oribatea. 



Char. Body and general habit those of 

 Galumna, but no wing-like appendages to 

 the pseudo-thorax. 



Two species ; not British (?). 



BIBL. Koch, Deutschl. Crustac. fyc. ; 

 Gervais, Walckenaer's Apteres, iii. 



HORMOSPORA, Brebisson. A genus of 

 Palmellaceae (Confervoid Algae), with a frond 

 consisting of simple or branched gelatinous 

 confervoid cords enclosing rows of oval or 

 spherical cells; they appear to the naked 

 eye like greenish filaments; found floating 

 among Confervae or other aquatic plants. 

 These plants do not appear to consist of 

 septate filamentous tubes like the Conferva, 



