( 443  ) 
XXI 1 1. — Observations  on  the  Injuries  sustained  by  certain  Plants 
from  the  attacks  of  Parasitic  Fungi ; with  particular  reference 
to  the  cause  of  the  Potato  Disease.  By  F.  J.  Graham,  B.A., 
F.L.S. 
Several  eminent  botanists  have  taken  great  pains  to  reduce  the 
various  tribes  of  fungi  into  their  proper  systematic  divisions ; but, 
except  in  a few  particular  cases,  sufficient  attention  has  not  been 
paid  to  the  injuries  which  those  of  a parasitic  nature  produce.  It 
is  not  to  be  wondered  at  therefore,  that  the  public  should  receive 
an  announcement  that  the  potato  was  destroyed  by  such  means, 
with  a certain  degree  of  incredulity. 
The  cereal  fungi  having  already  been  ably  treated  of  by  Pro- 
fessor Henslow  in  this  Journal,  it  will  scarcely  be  necessary  for 
me  to  make  a remark  upon  them.  Uredo  rubigo — Rust  (fig.  1) 
first  appears  on  the  blades  of  wheat  in  spring ; and  several  cir- 
cumstances favour  the  opinion  held  by  the  above  learned  pro- 
fessor, that  it  is  merely  an  early  stage  of  Puccinia  graminis.  It 
is  found  on  the  same  blade — is  nearly  of  the  same  colour,  and  is 
also  found  frequently  with  short  pedicels.  In  a beautiful  engrav- 
ing bv  Edwards,  executed  for  the  late  Sir  Joseph  Banks,  rudi- 
ments of  these  are  shown  both  above  and  below  the  surface ; but 
the  globular  sporidia  appear  to  be  thrust  off  by  each  other  in 
consequence  of  growing  in  such  dense  heaps.  Some  specimens 
of  Puccinia  graminis,  which  I have  seen  and  drawn  (fig.  2),  con- 
tain bodies  within  their  sporidia,  exactly  resembling  common 
forms  of  uredo.  On  the  other  hand,  the  uredo  is  usually  dis- 
persed in  spring,  and  whether  it  be  an  early  form  of  Puccinia  or 
not,  I believe  its  sporules  are  perfectly  capable  of  vegetating  in  that 
stage  of  growth.  Uredo  leguminosarum,  on  the  bean,  is  nothing 
more  than  the  sporidia  of  Puccinia  faba?,  having  no  independent 
sori ; and  Uredo  rosae  certainly  passes  into  Aregma  mucronatum, 
on  rose  leaves,  which  is  the  same  as  A.  gracile — on  those  of  the 
raspberry.  My  last  figure  of  Puccinia  graminis  has  also  nearly 
the  same  structure  as  this  Aregma. 
Puccinia  graminis — Red  gum  (fig.  2),  by  bursting  through  the 
epidermis  of  the  sheaths  and  stems  of  wheat,  tears  it  into  strips ; 
and  by  intercepting  the  natural  supplies  of  the  grain,  causes  it  to 
become  light  and  inferior.  Sir  Joseph  Banks  states,  that  in  con- 
sequence of  its  prevalence  in  1805,  a sack  of  wheat  did  not  yield 
more  than  a stone  of  flour.  It  is  first  of  a reddish  colour,  but 
afterwards  turns  black. 
Uredo  caries — Bunt  (fig.  3)  occupies  the  ovary  of  the  grain  of 
wheat  from  an  early  period;  and  as  this  expands  it  becomes  filled 
with  the  large  dark  globular  sporidia  of  the  f ungus,  instead  of  flour  ; 
to  which,  when  ground,  it  imparts  a rank  foetid  odour.  The  ears 
