ACHLYA. 



ACHNANTHES, 



times equal tlie sporange in length by the 

 time the latter discharges its contents j then 

 this branch becomes developed as a spo- 

 range, either at its summit or in its whole 

 length, or, when the branch is very short, 

 the portion of the main tube below the first 

 septum becomes a sporange. Sporanges of 

 a- third rank may succeed to those of the 

 second rank, and so on, until the plant has 

 exhausted the supply of food at its service. 

 In another form the active gonidia are pro- 

 duced at once in the sporanges, without the 

 intervention of secondary cells ; and then 

 they begin to move even before leaving the 

 parent sac. 



Aclilya prolifera also produces, though 

 more rarely, globular or spindle-shaped spo- 

 ranges, either terminal or borne on special 

 short lateral branches, in which are deve- 

 loped resting spores, characterized by a 

 larger size, double cell-membrane, and by 

 the absence of the cilia and consequent 

 motion. The mode of their development is 

 similar to that of the active gonidia ; but 

 they are much fewer in number, sometimes 

 as many as twenty, sometimes only four, 

 three, two, or even one being present in a 

 sporange. When a number occur in a 

 spindle-shaped sporange, they are ranged in 

 two rows, alternately, so that each is par- 

 tially interposed between its two opposite 

 neighbours. Their diameter varies from 

 1-1250 to 1-750 of an inch, the colour brown- 

 ish, displaying numerous oil-drops in the 

 granular contents when mature. The spo- 

 ranges producing them display a number of 

 round orifices when the spores are ripe ; but 

 the spores appear to escape by the decay of 

 the walls. These resting spores may remain 

 unchanged in water for a long time when no 

 suitable nidus exists, but will quickly ger- 

 minate if a dead insect or similar object be 

 thrown in. 



The resting spores are from 1 to 20, while 

 the active gonidia are from 5 to 150, the 

 number depending in each case on the size 

 of the sporange, not upon the size of the 

 spores or gonidia, which is tolerably regular. 

 Pringsheim states that starch occurs in 

 the contents of the resting spores of S. 

 ferax. 



A third form of reproductive organ is 

 described by Cienkowski, which in the 

 earlier stages resembles a sporange of rest- 

 ing spores j but the spores produce each a 

 long tubular neck, which bores through the 

 wall of the sporange and discharges its con- 

 tents as minute swarming bodies into the 



water ; these have not been seen to germi- 

 nate. These flask-shaped bodies resemble 

 the formations seen by Carter in SPIRO- 

 GYBA; and we have seen them in other 

 Algae. Al. Braun at first described them 

 as a species of CHYTRIDIUM, but subse- 

 quently has expressed an inclination to 

 regard them as antheridial spores of 

 Aclilya. 



In addition to the above, Al. Braun has 

 described curled tubular processes, resem- 

 bling the horns of Vaucheria, associated with 

 the sporanges in which resting spores are 

 formed; and he is inclined to regard them 

 as anthet'idia exercising a fecundating office, 

 like the horns of Vauclieria. Similar bodies 

 have been recorded in other Saprolegnice, 

 especially in Aclilya cornuta. (See PI. 27. 

 figs. 22-27). 



A. lignicola is found upon wood in water. 



BIBL. A description of the supposed species 

 will be found in Kiitzing's Sp. Algarum, 

 p. 159. For further information on the de- 

 velopment, see Al. Braun's Rejuven. (Ray 

 Society, 1853, pp. 188, 268) ; Pringsheim, 

 Nova Acta, xxiii. pt. 1. p. 397-460, 1852 ; 

 Anton de Bary, Sot. Zeit. x. p. 473, 1852 ; 

 linger, Linncea, 1843, p. 129 (Ann. d. Sc. 

 Nat. 3 me ser. ii. p. 5. pi. 1, 1844) ; Meyen, 

 Pflanzenpliys. iii. 457 ; Nageli. Zeitschr.filr 

 Wis. Bot. heft 1, p. 102, heft 3, 4, p. 28 

 (Ray Soc. 1845, p. 278, 1849, p. 101) ; Thu- 

 ret, Ann. d. Sc. Nat. 3 me ser. t. xiv. p. 20, 

 p. xxii, 1851 j Ch. Robin, Veget. Paras. 2nd 

 edit. 1853, p. 372 ; Varley, Tr. Mic. Soc. 

 iii. ; Cienkowski, Bot. Zeit. xiii. p. 801 ; Al. 

 Braun, Chytridium, Abh. Berlin. Ak. 1855 ; 

 Verjung. in d. Natur, p. 318 (Ray Society, 

 1853, p. 298). A list of all the writers who 

 had treated of Aclilya before 1843 is sub- 

 joined to Unger's Essay in the Linncca ; 

 Pringsheim, Jahrb. Bd. 1. heft 2, bd. 2. heft 

 2; Archer, Qu. Mic. Jn. 1867, p. 126 ; 

 Sachs,j5o. 1874, p. 276 ; Pfitzer, Monatsber. 

 d. Berl Akad. Mai 1872 ; Grevillea, March 

 1878 (woodcuts). 



ACHNAN'THES, Bory. A genus of 

 Diatomacege (Cohort Achnanthese). 



Char. Frustules compressed ; either sin- 

 gle, in pairs, or united into a straight fila- 

 ment ; geniculate in front view, without 

 septa j attached by a stipes fixed to one an- 

 gle ; uppermost valve with a longitudinal 

 median line, lowermost with a longitudinal 

 line, and a median nodule or stauros. 



The individual frustule, when single, or 

 the lowermost when they are united, is 

 furnished with a stipes or stalk, arising 



