ACHNANTHIDirJM. 



[ 10 ] 



ACHORION. 



from one end of the lower margin. Side 

 view of frustules elliptical, oblong or limnir, 

 sometimes slightly constricted in the mid- 

 dle ; markings of upper and lower valves 

 ditlerent, the upper (PL IG. fig. 2) exhibit- 

 ing transverse rows of dots (appearing like 

 striaj under a low power) interrupted by a 

 longitiulinal line, the lower (PI. 16. fig. 3) 

 being also furnished with transverse rows 

 of dots, interiupted by a stauros, as also by 

 a longitudinal line which in some has a no- 

 dule at each end. The valves being much 

 compressed, the transverse rows of dots ap- 

 pear also in the front view. The hoops 

 exhibit faint longitudinal and sometimes 

 transverse striae. 



Achnnnthes resembles Striafella in its 

 stalked flag-like filaments, but may be known 

 from it by the absence of internal siliceous 

 plates or vitta3. 



Species : — 



Freshwater; markings faint (minute) A.exilis*. 

 Marine or brackish water; markings 

 di-itinut. 



Stipes longer than frustnles A. lonffipes^. 



Stipes shorler than iVustules. 



Ends of valves acute A. brevipes. 



Ends of valves obtuse A. subsessilis, 



* PI. 16. fig. 4. t PI. 16. fig. 1. 



Kiitzing enumerates 15 species oi Ach- 

 nanlhes. 



BiBL. Ralfs, Ann. N. Hist. xiii. 489; 

 Kiitzing, Bacill. p. 75, & Sp. Alg. p. 54 ; 

 Smith, Brit. Dial. ii. 25 ; Eabeuhorst, Fl. 

 Alq. 109. 



ACIIXANTIIIDIUM, Kiitz.— A genus 

 of Diatomacete (Cohort Achnanthea^). 



Char. Those of Achnanthes, mostly tin- 

 gle, and Avithout the stipes. 



Five British species ; freshwater : — 



Filament of numerous frustules ... A. lauceolatum. 

 Fru^tulcs few, valves constricted 



in middle A. coarcialum. 



Frustules few, often straight; valves 



einstricted ue.arthe end A. microcephalum* . 



Frustules few; valves obtuse, ua- 



coustricted A. lineare. 



Frustules few, median line sigmoid A.JIexeUum^. 



* PI. 16. %. 5. t PI. 1<3- i!g- t5. 



Frustules very small, and markings very 

 faint. 



BiiiL. Smith, Brit. Diat. ii. 30 ; Kiitzing, 

 Bacill. 75, & Sp. AI(/. 5."}. 



ACIIO'lilOX, I.'ink and Komak.— The 

 generic name applied to one of the vegeta- 

 bles occurring in Fams, and characteristic 

 of that disease of the skin (also called 

 Porriyo or Tiiieci favosa). The structure of 

 the plant, Achorion Schoenleinii, bears 

 much resemblance to that of the genus 



Torula ; but it occui-s in definitely bounded 

 patches having a special arrangement of 

 the microscopic elements of which it la 

 constituted. 



Much has been written by medical authors 

 regarding these bodies ; but we shall not 

 enter into this part of tlie subject here, fur- 

 ther than to state that the presence of this 

 vegetable structure seems to be essential 

 and causative in the disease of the skin to 

 which we have alluded. Remak was unable 

 to make any of the spores germinate in or 

 on animal substances ; some however emit- 

 ted prolongations when placed upon an 

 apple; but the surface then decayed and 

 turned brown -watliin the week, and became 

 covered with mildew (Peuicillium f/laucum) . 

 One of the entire corpuscles kept upon the 

 arm for several days, fell off without leaving 

 any mark; but a fortnight after a /Vav/^ began 

 to be developed. Gruby states that he inocu- 

 lated various parts of the body with it, and 

 even caused it to grow upon wood(?). Ben- 

 nett ultimately confirmed the statements of 

 Gruby as to the inoculation. 



-Unfortunately, most authors who have 

 written on the parasitic fungi which occur 

 in morbid conditions of the human frame, 

 or are productive of disease, have not been 

 well acquainted with either Fungi or Algse. 

 Numberless names have been assigned to 

 them ; and in consequence, while many of 

 these organisms have been considered Al- 

 gfe, they have been regarded by others as 

 Fungi. It is, however, probable that all of 

 them are mere conditions of the most uni- 

 versally difYused species of Pcnivillium, As- 

 pcrf/illits, Jl/icor, or Cladosporium — genera 

 which are ca])able of propagation by cells 

 thrown off from the threads, other tlian the 

 norn)al fruit. It is quite impossible that, 

 as supposed by Ardsten, such a genus as 

 Fuccinia could be produced on animal 

 tissues. 



BiBL. Ch. Robin, Vcf/. parasites, 1853, 

 (plates, 2nd edit.) ; Bennett, Month. Jn. 

 Med. Sc. 1850 (tigs.), and Tr. Boy. Sac. 

 Edinh. 1842, XV. pp. 227-294; Gruby, 

 Compt. Bend. 1841, xiii. p. 72; Mycodermes 

 8^c., ihid.. o09 ; Tinea favosa, Midler's Ar- 

 chiv, 1842, p. 22; Hannover, MiUIer's Arch. 

 1842, p; 281-295, pi. 15. hgs. 7-9; Miiller 

 and Retzius, Midi. Archiv, 1842, p. 192, pi. 

 8 and 9 ; Lebert, Phi/. Path. ii. p. 477, Paris, 

 1845 ; Reniak-, Diaqn. u. pathoqen. Unters. 

 Berlin, 1845,p. 193-215 ; Bazin,"Zes Teiqnes, 

 Paris, 1853, 8vo (plates) ; Robin, Micr. 

 1877, p. 8(30. 



