PHYSODICTYON, 



[ 507 J 



PILOBOLUS. 



species, P. cochJeariforme, a large plaut, 

 growing iu purple tufts 4 to 6" long, on 

 moors aud among rocks in Ireland and the 

 Scotch highlands. 



BiBL. Hook. Brit. Flor. ii. pt. 1. p. 119; 

 Br. Jim(i. p. G8 : Eiu/l. Bof. pi. 2500 ; Elcart, 

 Si/?iops. Jintf/. pi. 5. hg. 40 ; Endlicher, Gen. 

 Plant. Suppl. 1. nos."472-81. 



PIiYS6DIC 'TYON, Ktz.— A genus of 

 Algse, consisting of globular vesicles com- 

 posed of angular parenchymatous cells con- 

 taining chlorophyll; diameter 1-12". On 

 rocks and submerged wood. P. qraniforme 

 (PI. 3, fig. 14). (Rabenhorst, Ahj. iii! 312.) 

 PHYSOM'ONAS, Kt.— A genus of Fla- 

 gellate Infusoria. Rounded, free or fixed by 

 a slender filament ; obliquely truncate in 

 front ; tiagella two, unequal ; diam. 1-3000" ; 

 freshwater and marine. (Kent, Inf. 263.) 



PHYTEL'EPHAS, R. and P.— The ge- 

 neric name of the Palm yielding the Vege- 

 table-Ivory nut. 



PHY^TOCRE'NE, Wallich.— An Arto- 

 carpaceous tree with wood of very remark- 

 able structure. See Wood. 



PHYTOP 'TID^.— A family of Acarina, 

 the nature of which is ill-understood. The 

 member? are found in the buds and gaUs of 

 plants. The galls, which form warts, tu- 

 bercles, nail-like growths (fcc. upon the 

 leaves, and produce distortion of the buds, 

 were formerly considered fungi, and placed 

 in the genera Urineum, Phillerium, &c. The 

 Acari are usually elongate, the body trans- 

 versely striated, the legs two anterior pairs, 

 the hinder pairs being replaced by tubercles 

 or long hairs. They were supposed to be 

 the larvae of Tetranychus or other Acaiiua, 

 but theu' eggs are found with them in the 

 galls. They have not been properly ar- 

 ranged iu genera and species, being usually 

 referred to the single genus Phytoptus, Duj , 

 They are often very transparent and easily 

 overlooked, and sometimes can only be 

 foimd by washing the opened galls, and 

 searching for them in the wash-water. 

 They are commonly met with in the galls 

 of the lime, the vine, the wiUow, the pear, 1 

 vew, &c., aud are named accordingly P. 

 "tilue (PL o3. fig. 24), P. vitis, &c. 



BiBL. Dujardin, Ann. Sc. Nat. 1857, iii. 

 lo ; Pagenstecher, Verh. Heidelb. 1859 ; 

 Frauenfeld, Verh. zool.-hot. G'es. Wien, 1864- 

 72; Low, ib. 1874; Thomas, Zeitschr. ge- 

 sammt. Naturw. xxxiii. ; Kaltenbach, 

 Pflam.feinde ; Briosi, M. M. Jn. xvii. 181 

 (with copious Bibl.) ; Ormerod, Inj. Ins. 

 179 ; Mui-ray, Ec. Ent. 365. 



PICO'BIA, Hall.— A genus of Trombi- 

 dina (Acarina). P. Heeri, in the subcu- 

 taneous cellular tissue of the woodpecker. 



Bibl. Megnin, Paras. 248; Haller, 

 Zeitschr. wiss. Zool. 1877, xxx. 



PIGGO'TIA, Berk, and Broome.— A 

 genus of Sphaeronemei (Stylosporous 

 Fungi), or perhaps the conidiiferous form of 

 Dothidea. P. astroidea occurs on the green 

 leaves of the elm, formino- ii-regidar round- 

 ish, granulated or wrinkled jet-black patches 

 (sometimes with a yellow border) on the 

 upper surface of the leaf. Perithecia soon 

 confluent, bursting by a lacerated fissure. 



Bibl. Berk, and Broome, Ann. N. H. 2. 

 vii. 9o, pi. 5. fig. 1. 

 PIGMENT. See Introduction, p. xxxiv. 

 PIGMENT-CELLS of connective tissue 

 occur in a few isolated spots only in Man 

 and the higher Vertebrata, but are widely 

 distributed m Amphibia and Fishes, appear- 

 ing especially in the skin, the serous mem- 

 branes, and the tunica adventitia of the 

 vessels. The pigment is deposited in gi-a- 

 nules, which differ in shape and colour. 

 The pigment-cells of connective tissue are 

 usually characterized by their beautiful 

 stellate form and numerous processes. In 

 Man they occur normally in the eye. The 

 pigment -granules in Amphibia are collected 

 in round masses or diffused in the stellate 

 cells, their movement being evident but 

 slow. Spontaneous alteration in form of 

 pigment-cells occurs in the skin of these 

 animals, and is connected with the change in 

 colour which they present. See Mel anine. 

 PILA'CRE, Fr.— A genus of Trichogas- 

 tres (Gasteromycetous Fimgi). 



This genus must not be confoimded with 

 0)iyyena, to which it bears a cei'tain resem- 

 blance. One or two of the species are 

 remarkable for the strong permanent odour, 

 resembling that of pigs. 



Bibl, Berk, and Broome, Ann. N. H. 2. 

 V. 365, pi. 11. 



PILEOLA'RIA, Cast. See Uromyces. 



PILEORin'ZA.— A conical hood on, or 



shield or guard to, the tips of the roots of 



plants, protecting the nascent tissue. See 



Root. 



PILINTA, KUtz.— A genus of Chaetc- 

 phoraceousAlgfe. Filaments erect, jointed, 

 tufted, rooting, forming a spongy stratum. 

 P. rimosa (PI. 3, fig. 15), on submersed 

 wood ; marine. (Rabenhorst, Alg. iii. 386.) 

 PILOBO LUS, Tode.— A geims of Mu- 

 corini (Phycomycetous Fungi), consisting 

 of little moulds growing upon dung ; bear- 



