12 
septum  exists  before  the  definitive  separati¬ 
on  of  the  new  cells,  it  lies  in  the  region  of 
constriction.  The  disappearing  of  the  septum 
coincides,  as  a  rule,  with  the  condensation 
of  the  chromatin  in  the  center  of  the  new 
cell. 
Besides  these  facts,  we  find  other  ones 
of  some  interest,  as  regards  the  reproduction. 
The  gemmation  is  the  general  form  of  cellu¬ 
lar  division  in  the  yeasts.  This  process,  a  va¬ 
riety  of  “septation”,  occupies  an  intermediate 
place  between  the  typical  gemmation  and 
the  true  septation  of  the  Schizosciccharomyces 
which,  according  to  some  mycologists,  con¬ 
stitutes  a  definite  group,  having  as  type  the 
Sacch.  ludwigii.  In  the  O.  brasiliense  the  gem¬ 
mation  is,  in  certain  conditions,  found  in 
human  and  animal  organisms  and  in  the 
center  of  some  cultures.  The  second  process, 
the  variety  “transversal  septation”,  is  found, 
almost  exclusively,  in  some  cultures  of  the 
parasite  and  in  certain  foci  in  human  lungs 
(preparation  made  after  87  days  of  culture  in 
Sabouraud).  It  is  often  easy  to  discover  one  of 
the  characteristicals  of  the  Oidia  at  the  ex¬ 
tremity  of  a  mycelium.  6  or  7  yeast  cells  are 
foil  owing  on  a  mycelian  element.  There  are 
forms,  though  rare,  which  we  must  consider 
as  terminal  chlam  ido  spores.  They  are  large 
spherical  yeast  cell  with  double  outline,  clear 
and  deeply  stained  protoplasm  and  termina¬ 
ting  unexpectedly  a  short  or  long  mycelium. 
There  are  also  intercalary  chlamidospores. 
If  the  preparations  turn  out  well,  the  yeast 
cells,  when  in  rest,  show  a  complicate  struc¬ 
ture  (preparation  after  87  days  of  culture). 
A  figure  of  such  forms  accompanies  this 
paper.  It  represents  a  detached  cell  with  frag¬ 
ments  of  the  viscous  border  still  at  the  pe¬ 
riphery.  The  protoplasm  is  of  pale,  and  the 
nucleus  of  deep  rose-colour.  Intensily  stained 
and  brilliant  granules,  seen  close  by,  are  me- 
tachromatic  granulations.  There  are  no  va¬ 
cuoles.  The  cellular  membrane  is  fine  and 
deep  red.  Sometimes  the  structure  is  more 
complicate.  There  is  an  elongated  cell 
with  thick  cellular  membrane,  excentric  vo¬ 
luminous  nucleus  and  broad  nuclear  mem¬ 
brane.  Within  the  nucleus  we  see  a  more 
deeply  stained  granule  and  by  its  side  meta- 
chromatic  granulations.  Here  also  we  find 
no  vacuoles.  When  such  appear  in  these 
forms  they  are,  in  our  opinion,  due  to  a  faulty 
technique. 
Mycelium. 
The  mycelium  of  the  Oidium  brasiliense 
shows  various  aspects.  The  mycelian  struc¬ 
ture  is  abundant  in  potatoe—  and  in  carrot- 
cultures,  but  not  all  cultures  of  the  parasites 
show  such  abundance.  As  a  rule,  at  first  the 
mycelia  do  not  exist  in  the  cultures  of 
the  fungus.  To  the  breadth  of  3  miera  we 
may  add  one  of  6  micra,  observed  in  old 
culture  forms  on  Sabouraud,  with  great  va¬ 
riety  of  granulations  and  showing,  someti¬ 
mes,  a  complete  endoconidium.  The  slender 
forms  are  found  indifferently  in  the  cultures. 
The  mycelium  is  wavy. 
In  the  water  of  carrot-culturetubes  we 
may  possibly  see  fine  and  long  mycelia  (run¬ 
ning  through  many  microscope  fields),  irre¬ 
gularly  divided  and,  at  intervals,  septate  (Pho- 
togiaph  taken  with  obj.  C,  ocul.  4  of  ZEISS). 
The  endoconidia  are  h  re  found  in  greater 
proportion.  We  accompanied  the  mycelium 
formation,  examining  the  stained  and  han¬ 
ging-drop  preparations. 
There  are,  in  our  opinion,  two  processes 
of  mycelium  formation.  Sometimes  from 
a  rectangular  element  with  large  nucleus 
and  deeply  stained  protoplasm  springs 
another,  also  rectangular,  though  more  elon¬ 
gate.  The  new  cells  stretch  successively  until 
a  true  mycelium  appears.  At  other  times  a 
large  cell,  either  spherical  or  oval,  gives 
growth  to  smaller  cells  and  forms,  after  some 
divisions,  a  true  mycelium.  In  this  case,  as  a 
second  variety,  the  mycelium  may  not  show 
any  gemformation  and  spring  directly  from 
the  round  cell.  Here  a  thickening  of  the 
cellular  membrane  is  often  seen  at  the  point  of 
emerging  of  the  mycelium.  The  distribution 
of  the  chromatin  in  the  mycelium  does  not, 
as  a  rule,  follow  well  defined  types.  Some¬ 
times  the  mycelium  presents  in  all  the  septa 
