POLLEN. 



[ 619 ] 



POLYCYSTINA. 



*** Outer coat with more than three 

 furrows, each with a pore. Some- 

 times abnormally, instead of three, 

 but normally in most of the Boragi- 

 nacese and Polygalaceae. 



**** Six to nine furrows, three con- 

 taining a pore : Lythraceae, Mela- 

 stoniaceae, Combretaceae. 



***** Three or four furrows, with six 



or eight papillae : Neurada procum- 



bens, fyc. 

 ****** Three furrows and three papillae 



not in the furrows : Carolinea cam- 



pestris, SfC. 



Starch-corpuscles exist in the fovilla of 

 some pollen-grains in the form of very small 

 grains which are stained blue by iodine. 



Related compound forms occur in the 

 Ericaceae and Epaciidaceae, where the grains 

 are tetrahedrally arranged (PI. 40. fig. 17). 

 Other aberrant forms occur in which the 

 single grains are cubic or dodecahedral ; 

 and in the Cichoraceae polyhedral forms of 

 complicated character are common (figs. 16, 

 27, 28). 



Mature pollen-grains should be observed 

 dry (as opaque and transparent objects), and 

 in water or glycerine ; in some cases, in oil ; 

 treatment with acids is also useful in making 

 out structure. In observing the develop- 

 ment of pollen, it is necessary to wet the 

 object with a solution of sugar or gum; 

 otherwise the appearances are altogether 

 changed through endosmotic action. 



BIBL. Nageli, Entwick. des Pollens, 1842, 

 and on Cell-formation, Ray Society, 1846, 

 1847 ; Hofmeister, Sot. Zeit. vi. 1848 ; 

 Gieswald, Linncea, xxv. 81 ; Schacht (Coni- 

 ferae), Beitrag z. Sot. 1854; Saccardo, 

 Nuovo Giorn. Sot. 1872 ; Hassall, An. N. H. 

 1841 & 1842 (pis.) ; Smith, M. M. Jn. xvii 

 9 (figs.); Edgeworth, Pollen, 1877 (446 

 figs.), & M. M. Jn. xviii. 190; Qu. M. Jn 

 1880, xx. 19; Warming, HansteirfsBot.Abh 

 1873. 



POLY AC 'TIS. Separated from Botrytis 

 on account of the dark, quasi-carbonizec 

 flocci. 



POLYARTHRA, Ehr. A genus o 

 Rotatoria, of the family Hydatinaea. 



Char. Eye single, cervical ; foot absent 

 body with six cirrhi or fins on each side. 

 Jaws each with a single tooth. 

 P. platyptera (PI. 44. fig. 19). Body 

 ovato-subquadrate, fins ensiform serrate 

 freshwater ; length 1-190". 



P. trigla. Fins setaceous; freshwater 

 ength 1-190". 



BIBL. Ehrenberg, Infos, p. 440. 

 POLYCLI'NUM, Sav. A genus of Tu- 

 nicate Mollusca, of the family BOTBYLLID.S: 

 [p. 115). 



P. aurantium. Consists of little rounded 

 orange masses, fixed to rocks by a short 

 and thick peduncle. 



BIBL. Forbes and Hanley, Br. Moll i. 

 14. 



POLYCOC'CUM, Sant. A genus of 

 Micro-lichens, parasitic on the prothallus of 

 Stereocaulon condensation. 



Char. Spores eight, small, bilocular, 

 brown. 



BIBL. Lindsav, Qu. Mic. Jn. 1869, 343. 

 POLYCOC'CUS, Kiitz. Probably be- 

 longs to Microcystis (Rab., Alg. ii. 55). 



POLYCO'PE, Sars. A bivalved Ento- 

 mostracon of the Cladocopa group. Upper 

 and lower antennae both natatory and seti- 

 ferous ; two pairs of posterior limbs, the 

 first natatory, the second branchial; no 

 eyes ; no heart ; intestine imperforate. 

 Valves circular, thin, smooth, or orna- 

 mented. Marine ; recent and fossil. 

 BIBL. Brady, Linn. Tr. xxvi. 470. 

 POLYCYS'TINA, Ehr. A family of 

 Radiolarian Rhizopoda. 



The animal bodies are contained in shells 

 of various forms (PI. 39. figs. 23-31). 

 These are rounded, conical, oval, radiate, 

 star-shaped &c., often furnished with spines 

 and other processes, and sometimes con- 

 stricted so as to give them a jointed ap- 

 pearance. The shells are siliceous, every- 

 where perforated by coarse, rounded or 

 angular foramina; and at one end, some- 

 times at both, is a larger aperture. The 

 animal matter is olive-brown or yellowish. 

 The Polycystina have been found on nearly 

 every ocean-bottom. Ehrenberg found 

 them at Cuxhaven, and in the Antarctic 

 seas ; Bailey in the depths of the Atlantic ; 

 Miiller in the Mediterranean, and Hackel in 

 the Adriatic ; Wallich in the Indian Ocean; 

 and Wyville Thomson, Carpenter, and 

 Gwyn Jeffreys in the deep-sea soundings of 

 the North Atlantic. The siliceous skeletons 

 or shells accumulated in thick deposits 

 during the last geological periods ; and 

 myriads of these exquisite microscopic forms 

 may be obtained from many strata in Sicily, 

 Greece, Oran, Bermuda, Richmond, Vir- 

 ginia, and Barbadoes. They are rare in the 

 Chalk. 



BIBL. Ehr. Monatsb. Berl Ak. 1846, 



