PHYLLOPODA. 



[ 696 ] 



PHYSIOTIUM. 



filaments found on distinct plants from the 

 spores; and 3. tetraspores, collected into 

 sori either towards the apex of the thallus 

 or on proper lobes. 



BIBL. Harvey, Mar. Alg. 142, pi. 18 A ; 



Phyc. Brit, pi." 191 ; Greville, Alg. Brit. 



pi. 15 ; Derbes and Solier, Ann. Sc. Nat. 3 



se"r. xiv. 277, pi. 37 ; Thuret, ibid. 4 se"r. iii. 18. 



PHYLLOP'ODA. See ENTOMOSTKACA. 



PHYLLOXE'RA, Fonsc. A genus of 



Aphidae (Homonterous Hemiptera) ; the 



species have the fore wings flat on the back, 



with 1 simple stigmal, and 2 simple oblique 



discoidal nerves ; the antennae 3-jointed. 



These insects are notable from the immense 

 damage they do, in the vinicolous countries, 

 to the grape-vines. The apterous broods 

 feed upon the roots of the vine, exhausting 

 its juices, producing decay of the leaves, and 

 absence of fruit. In the autumn, the winged 

 sexual forms are produced, which spread the 

 malady abroad, by laying their eggs in new 

 places. P. vastatrix (PI. 53. fig. 7) is the 

 vine-pest ; but other species occur on the 

 oak, &c. The insects may be found by 

 separating the layers of the roots, and 

 examining them with a good lens, when 

 they will be seen in all stages, often sur- 

 rounded with a zone of eggs. 



BIBL. West wood, Intr. ii. ; Fatio and 

 Demole-Ador, Rap. s. 1. Phyll. 1875-76; 

 Lichtenstein, Ann. Agronom. 1876, ii. 129 ; 

 Robin, Micr. 1877, 953; Balbiani, Rev. 

 Scient. 1874; Cornu, Phyll. vast., 1878 

 (24 plates). 



PHYMATOP'SIS, Tul. A genus of 

 Microlichens parasitic on the apothecia 

 and thallus of Usneae. 



BIBL. Lindsay, New-Zealand Lich. and 

 Fungi, 442 ; Qu. Mic. Jn. 1869, 350. 



PHYSAC'TIS, Kiitz. A genus of Oscil- 

 latoriaceae (Confervoid Algae), improperly 

 separated from Rivularia, consisting of 

 freshwater and marine plants, growing on 

 stones &c., at first globose, and afterwards 

 vesicular and lobed by peripheral growth 

 accompanied by gradual decay of the ori- 

 ginally solid centre. Under this head are 

 included : 



P. (Rivularia) nitida. Deep olive-green, 

 tufted and lobed, gregarious ; fronds from 

 1-12 to 1" in diameter. (R. bullata, Berk.) 

 Marine, 



P. (Riv.) plicata. Diam. 1-12 to 1-2" in 

 diameter ; deep green. Marine. 



P. (Riv.) pwum. Globose, dirty green, 

 1-12 to 1-2" in diameter. Freshwater. 



BIBL. Ktitz. Sp. Ala. 332; Tab. Phyc. 



Bd. i. pi. 58; Hassall, Fr. Alg. 262 ; Har- 

 vey, Mar. Alg. 222 ; Berk. Gleanings, pi. 2. 

 fig. 1 ; Rabenh. Alg. ii. 206. 



PHYSA'RUM, Pers. A genus of Myxo- 

 mycetes, containing numerous species 

 growing on rotten wood, bark, leaves, &c. 

 They are nearly related to Didymium and 

 Didcrma, but liave a simple membranous 

 peridium : the filaments are adnate to the 

 peridium; but in some spores they are 

 very few, approaching to the condition of 

 Licea. Some are sessile, others stipitate 

 (fig. 569) ; the clustered forms (P. hi/ali- 



Fig. 571. Fig 



Fig. 670. 



Physarum bryophilmn. 



Fig. 569. Plants growing on a Plagiochila. Magn. 2 

 diams. 



Fig. 570. A peridium burst. Magn. 25 diams. 



Fig. 571. Filaments and spores from the same. Magn. 

 100 diams. 



num and utriculatuni) are removed to 

 Berkeley's genus BADHAMIA. P. album is 

 common. 



BIBL. Berk. Br. Fl. ii. pt. 2. 314 ; Mag. 

 Zool. and Bot. i. 49 ; Ann. N. H. vi. 431, 

 2. xiii. 159 ; Fries, System. Myc. iii. 127 ; 

 Sum. Veg. 153 ; Greville, Crypt. Fl. pi. 40. 

 310; Cooke, Grevilka, 1880; Kent, Pop. 

 Sc. Rev. 1881, and Inf. 470. 



PHYS'CIA, Nyl. Like Parmelia, but 

 with the spores bilocular ; many species. 



PHYSCOMIT'RIUM, Bridel. A rams 

 of Funariaceae (Acrocarpous Mosses;, in- 

 cluding many Gymnostoma of other authors. 

 P/iyscomitrium pyriforme, Brid.= 6r?//fto- 

 stomum pyriforme, Hedw. Ph. spharicum 

 is remarkable as having been found only in 

 one year in one locality in Britain. 



This species exhibits a pretty structure in 

 a vertical section of the immature capsule, 

 the mass of sppriferous tissue being sus- 

 pended freely in the middle by cellular 

 threads. 



PHYSIO'TIUM, Nees. A genus of Juu- 

 germannieae (Hepaticae), containing one 



