ASCOMYCETES. 



ASELLUS. 



being sometimes simple, in others very com- 

 plicated. 



The sporanges of the Helvellacei vary much 

 in form, the simpler resembling closely 

 some of the Phacidiacei; some kinds are 

 minute fleshy cups lined with asci forming a 

 superficial layer, as in Propolis, or they are 

 large fleshy cups raised often on a stalk 

 (Peziza), these cups being closed at first, but 

 opening widely afterwards. In the Helvellce, 

 the cup is converted into a stalked mitre- 

 shaped body clothed above with asci. Others 

 are of columnar form, thickened at the sum- 

 mit, which is clothed with the asci, as if a 

 cup-shaped receptacle had been turned down 

 over it (Spathulea, fig. 39), this thickened 

 head becoming more considerable and exca- 

 vated into little pits in Morchella. These 

 plants are mostly found on the ground or 

 decaying vegetable substances, in damp 

 places, and are frequently of gelatinous con- 

 sistence. 



If a Peziza, Morchella, a Rhytisma aceri- 

 num, or similar Fungus, in its last stage of 

 development, is kept shut up in a bottle for 

 several hours, and then gently taken out, 

 the contact of the external air causes an 

 immediate and abundant explosion of spores, 

 which may be collected on slips of glass for 

 microscopic examination. If care is taken 

 in the experiment, it will be found that a 

 considerable quantity of a colourless liquid is 

 expelled with the spores, which liquid con- 

 tains minute molecules, and evaporates very 

 rapidly, leaving more or less apparent spots 

 on the glass. 



Synopsis of the tribes : 



1. HELVELLACEI. Sporange fleshy, of va- 

 rious forms, ultimately expanded, clavate, ca- 

 pitate, stalked, mitre-shaped, cup-shaped or 

 bell-shaped, the upper surface clothed by elon- 

 gated sacs (asci), each containing eight 

 simple or septate spores. 



2. TUBERACEI. Sporange (subterraneous) 

 globular, with an adherent peridium; solid 

 and fleshy within, and excavated sinuously 

 into numerous cavities clothed by asci 

 containing four or eight spores ; the internal 

 mass drying up or becoming pulverulent or 

 floccose when mature. 



3. PHACIDIACEI. Sporange fleshy, sim- 

 ple or branched, more or less cup-shaped in 

 the sporiferous region, which opens widely or 

 by a slit when mature, and exposes a cavity 

 lined with elongated asci mixed with para- 

 physes. 



4. SPH^ERIACEI. Sporanges usually col- 

 lected on a common, usually horny, receptacle, 



opening by a terminal pore into a cavity lined 

 with asci. 



5. PERISPORACEI. Common receptacle 

 floccose, radiating from a centre, bearing a 

 globular sessile conceptacle, opening by a 

 terminal pore, and irregularly lined with asci 

 filled with simple ovate spores. 



6. ONYGENEI. Mycelium floccose, bearing 

 capitate, stalked sporanges, which open by a 

 circular slit at the base, causing the upper 

 part to fall off like a cap ; exposing a spori- 

 ferous structure composed of interlacing 

 branched filaments, bearing globular asci 

 at the free extremities of the branches. 



BIBL. See under the heads of the Tribes. 



ASCOPHORA, Tode. See MUCOR. 



ASCOTRICHA, Berk. A genus of Peri- 

 sporacei (Ascomycetous Fungi), containing 

 one species. 



A. chart arum, a kind of mildew growing 

 on paper, forming a brownish, angularly 

 and dichotomously branched mycelium, from 

 which arise globose, black hairy peridia con- 

 taining linear asci, each containing a single 

 row of chocolate-coloured spores. Peridia 

 from 1-20" to 1-30" in diameter. 



BIBL. Berkeley, Ann. Nat. Hist. i. 257. 

 pi. 7. fig. 8. 



ASCUS. The term applied to the cylin- 

 drical or clavate tubular sac forming the pa- 

 rent cell of the spores in the Ascomycetous 

 or Thecasporous Fungi. It is frequently 

 called a theca also (figs. 40 and 42). See 

 ASCOMYCETES. 



ASELLUS, Geoftroy (the aquatic wood- 

 louse). A genus of Crustacea, of the family 

 Isopoda. 



Char. Antennae four, outer much longer 

 than the inner ones ; legs shorter than the 

 body, the first pair terminated by a minute 

 subcheliform hand, the others by a simple 

 hook or claw; two abdominal jointed append- 

 ages, each terminated by two elongate and 

 jointed filaments. 



A. vulgaris. Length 1-4 to 1-2" or more. 

 This animal is particularly interesting to the 

 microscopist, on account of its forming the 

 most readily procurable object for examining 

 the dorsal vessel and circulating liquid in 

 motion. It is found in almost all stagnant 

 waters. The two currents of the circulating 

 liquid, with the colourless corpuscles, are 

 readily seen streaming through every part of 

 the body. Beneath the large scutiform 

 joint of the body (the abdomen), are three 

 flattened branchial false legs or gills on each 

 side, each protected by a gill-cover; these 

 are in constant motion during life. 



F2 



