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- 

 naceie and Polygalacea;. 



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

 taining a pore : Lythraceaj, Mela- 

 stomacea3, Combretacese. 



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

 or eight papilliB : Neurada promm- 

 hens, ^-c. 



****** Three furrows and three papillfe 

 not in the furrows : Carolinea cam- 

 pesfris, Sfc. 



Starch-corpuscles exist in the fovilla of 

 some pollen-grains in the form of very small 

 grains which are stained blue by iodiue. 



Related compound forms occur in the' 

 Ericacefe and Epacridacete, where the grains 

 are tetrahedrally an-auged (PL 40. fig. 17). 

 Other aberrant forms occm- in which the 

 single grains are cubic or dodecahedral ; 

 and in the Cichoracese polyhedral forms of 

 complicated character are common (figs. 16, 

 27, 28). 



Mature pollen-grains should be observed 

 drv (as opaque and transparent objects), and 

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

 treatment with acids is also useful iu 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. Nfigeli, Enticick. des Pollens, 1842, 

 and on Cell-formation, liai/ Society, 1846, 

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

 Gieswald,inni«?«, XXV. 81; Schacht (Coni- 

 ferse), Beitrag z. Bot. 1854 ; Saccardo, 

 Kuovo Giorn. Bot. 1872 ; Ilassall, An. N. H. 

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

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

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

 1880, XX. 19; V^^&rmmg, Uansteins Bot. Abh. 

 1873. 



POLY AC'TIS.— Separated from Botrytis 

 on account of the dark, quasi-carbonized 

 flocci. 



POLYAR'THRA, Ehr.— A genus of 

 Rotatoria, of the family Iljdatinsea. 



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. trifjla. Fins setaceous ; freshwater 

 length 1-1 no". 



BiBL. Ehrenberg, Infus. p. 440. 

 POLYCLI'NUjNI, Sav.— a genus of Tu- 

 nicate Mollusca, of the family Botkyllid^ 

 (p. 115). 



P. aurantmm. 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 

 Stcreocaulon eondensatum. 



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- 

 mo.stracon of the Cladocopa group. Upper 

 and lower antennae both natatory and seti- 

 ferousj two pairs of posterior limbs, the 

 first natatorj', the second branchial; no 

 eyes ; no heart ; intestine imperforate. 

 Valves circular, tliin, smooth, or orna- 

 mented. Marine ; recent and fossil. 

 BiBL. Brady, Linn. Tr. xxvi. 470. 

 POLYC YS'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 foimd 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 Hiickel in 

 the Adriatic; Wallich in the Indian Ocean; 

 and Wyviile Thomson, Carpenter, and 

 Gwvn Jeftreys 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. Monatsh. Berl. Ak. 1846, 



