* 
disseminated. The pustules (called sori) are collections of spores,  < 
A 3 ° . : ri aie 
they are frequently found intermingled in the same pustule, andare. 
a 
ure and function. The stalks which bear them are stronger and do — 4a 
‘the smut and conaeauently Kes received less attention from p 
-calmen. Its life history Feb! 
- several related species have been studied very fully. The best prac- 
tical article upon it in English is that by Mr. ©. H. Peck in his 
served is confined to the foliage, where it appears as small pustules. ar 
It easily falls. . The shape is nearly spherical (Plate XVI, Fig. 2),and — 
- i her ; 3 ; v4 \ a3 
shit od : ee ra i SH et igi a ey ag 15 
/ REPORT OF THE COMMISSIONER OF AGRICULTUR 
aq te th 
as not been especially studied, but tha 
thirty-fourth report. 
(6) EXTHRNAL APPEARANCE, 
. Corn rust is very similar to the rust of wheat, but still specifically 
distinct. It does not grow upon the floral organs, but so far as ob- 
After the middle of the summer the pustules begin to appear on — 
either or both surfaces of the leaves. At first they are covered by 
the epidermis and are whitish, but they soon swell sufficiently to - 
break the latter, whose lacerated edges may be seen standing up 
around them. Thus the pustules become exposed, and at thesame § ~ 
time the spores which they contain are matured and readyto be 
Thesori are roundish, or oftener somewhat elongated in form, seat- 
tered irregularly; but sometimes they are clustered, andthentheytend 
to be arranged in lines parallel to the length of the leaf. ge 
The earlier pustules, if examined carefully, will be found of a. 
bright, rich, yellowish-brown, color; the later ones almost black, kos 
(¢) THE FUNGUS. : Ay 
This difference in color indicates two different kinds of spores; but | 
roduced from the same vegetative fungus threads (mycelium) within 
he leaf. The brown spores (uredospores), which are the earlier, 
correspond to the so-called red rust of the wheat. Asectionthrough  — 
a pustule shows that each sporeis borne on a slender stalk, from which 
> 
the comparatively thick wall or coat of the spore is covered with 
minute projections. The diameter isabout one one-thousandth of an 
inch ora trifle more. In the protoplasmic contents drops of oil are . — 
sometimes seen. The vitality of the spores is of short duration. - 7 
They must germinate within a limited time if at all. His believed 
that they are killed by becoming dry, and that they do not survive 
the winter. The black pustules (Piate X VE, Fig. 1)arecomposed of 
dark-colored spores eee having a very different struct- 
not separate from them. Each spore is broadly elliptical in outline, — 
with both ends rounded, or with the apex oecasionally thickened and wert 
pointed (Plate XVI, Fig. 5). Thesurfaceissmooth. <A partition is 
placed across the middle which divides the interior of the spore into + __ 
two cavities. At germination each part may germinate independ- 
- ently, so that this may be called adoublespore. At the partition the 3) 
spore is constricted and it is twice as long as broad; some area half ~~ 
longer and broader than others, and the largest are a littlenarrower 
than. the diameter of the uredospores, They measure .0006 to .0009 
inch by .0012, to .0018 inch. These may be called resting spores, be- 
cause they remain dormant through the winter and germinate the 
next season, again producing the rust and thus perpetuating its ex- 
t 
such as the common wheat rust produces upon the barberry. 
istence. It is not known to have any third form of spores (ecidium) 
