PHYSIOTIUM. 



[ 505 ] 



PILOBOLUS. 



PHYSIOTIUM, Nees.— A genus of Jun- 

 germannieae (Hepaticaceae), containing one 

 species, P. cochleariforme, a large plant, 

 growing in pinple tufts 4 to 6' long, on 

 moors and among rocks in Ireland and the 

 Scotch highlands. 



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

 Br. Jung. p. 6S, Engl. Bot. pi. 2500; Ekart, 

 Synops. Jung. pi. 5. fig. 40; Endlicher, Gen. 

 Plant. Suppl. 1. nos. 4/2-18. 



PHYSOMYCETES.— An order of Fungi 

 composed of microscopic plants of very 

 simple organization, the mycelium being a 

 byssoid or flocculent mass, bearing simple 

 vesicular sporanges {peridiola), filled with 

 minute spores. The nature of the membra- 

 nous wall of the peridioles is not yet well 

 ascertained in all the genera, some authors 

 describing it as merely a veil, others as a 

 perfect sac formed by the expansion of the 

 terminal cell of the filament, which is cer- 

 tainly true in Mucor. According to our own 

 observations, the spores are formed by free- 

 cell-formation in the peridiole which ulti- 

 mately bursts to discharge the spores. 



The distinction between the two families 

 seems to depend chiefly on the conditions of 

 the peridioles. 



In the Antennariei, where they are firmer, 

 they are sessile on radiating flocci, which 

 sometimes send processes which grow^ up 

 and surround them, or they are attached 

 to the sides of erect filaments; these fila- 

 ments form whitish or greyish patches, on 

 the leaves of trees and herbs, bearing a close 

 external resemblance to Erysiphe. 



The Mucorini are moulds growing on de- 

 caying organic matter, the mycelium consti- 

 tuting flocks floating in liquids or overgrow- 

 ing damp substances, while the delicate spore- 

 sacs or peridioles are borne at the apices of 

 erect stalk-like, and often extremely branched 

 filaments. The genus Sizygites exhibits a 

 remarkable peculiarity, according to Ehren- 

 berg, for he states that each spore-sac is 

 formed by means of the conjugation of two 

 branches of the ramified fructification (see 

 Sizygites). 



Recent observations on some of the plants 

 of this order seem to indicate that, as in 

 most of the divisions of this class, much 

 remains to be cleared up concerning the 

 relations of the forms. See on this subject 

 the article Eurotium, which genus, accord- 

 ing to De Bary's researches, seems to be 

 associated as merelvone form of fructification, 

 with Aspergillus, upon the same myce- 

 lium. 



Synopsis of the Families. 



1. Antennariei. Mycelium filament- 

 ous, radiating, or erect, bearing sessile, glo- 

 bular, membranous sacs (j)eridioles), filled 

 with ovate spores, discharged by the rupture 

 of the sac at its apex. 



2. Mucorini. Mycelium filamentous, 

 vague, giving ofi^ erect, simple or branched 

 filaments terminating in vesicular cells {peri- 

 dioles) filled with minute spores; often wdth 

 a central column in the interior. 



BiBL. See the genera. 



PHYTELEPHAS, R. and P.— The ge- 

 neric name of the Palm yielding the Vege- 

 table Ivory nut. 



PHYTOCRENE, Wallich.— An Artocar- 

 paceous tree with wood, of very remarkable 

 structure. See Wood. 



PIGGOTIA, Berk, and Broome. — A 

 genus of Sphseronemei (Coniomycetous 

 Fungi), or perhaps the conidiferous form of 

 Dothidea. P. astroidea occurs on the green 

 leaves of the elm, forming irregular, 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 Br. Ann. Nat. Hist. 

 ser. 2. vii. p. 95. pi. 5. fig. 1. 



PIGMENT. See lNTRODucTioN,p.xxix. 



PILACRE, Fr.— A genus of Trichogas- 

 tres (Gasteromycetous Fungi). 



BiBL. Berk, and Br. Ann. Nat. Hist. 

 2nd ser. v. p. 365. pi. 11. 



PILOBOLUS, Tode.— A genus of Mu- 

 corini (Physomycetous Fungi), consisting of 

 little moulds growing upon dung; bearing 

 some resemblance in their structure to 

 Botrydium among the Alga3. The plants have 

 a stoloniferous creeping mycelium, from 

 which arise fertile pedicels, each cut off" from 

 the mycelium by a septum ; the upper part 

 of the pedicel expands into the vesicle, which 

 also becomes shut ofl" by a septum ; in the 

 vesicle or peridiole spores are next developed 

 by free cell-formation, and at the same time 

 the septum becomes pushed up into its 

 interior (as in Mucor) to form a columella, 

 which ultimately causes the vesicular peri- 

 diole to split ofi^ by a circumscissile dehis- 

 cence just above the septum ; it is thrown 

 off" with elasticity, enclosing the spores. The 

 development of P. crystallinus has been 

 studied by Colin. He finds the germinating 

 spore to i)roduce a creeping unicellular 

 mycelial portion, and next a fruit-pechcel, 

 which soon has the peridiole separated by a 



