TAXONOMY 
219 
detached from the pedicels and blown by the wind to healthy plants. 
After summer is over and dry weather comes on, an examination of 
stubble in the field (blades of grass and stems of wheat left carelessly), 
these rust-red lines are replaced by brownish-black spores called 
teleutospores (teliospores). A mass of these is known as a telium. 
The summer stage on wheat is known as Uredo linearis. 
The autumn stage on wheat is known as Puccinia graminis. 
Fig. 97. — Spore forms of wheat rust, Pucainia graminis. A, Section through 
barberry leaf showing pycnia on upper surface and aecia on lower; B, two uredinio- 
spores; C, germinating urediniospore ; D, teliosorus showing several teliospores; 
E, single two-celled teliospore; F, germinating teliospore with four-celled basidium 
and two basidiospores; G, basidiospore growing on barberry leaf. ( Harshberger , 
adapted from deBary.) 
The teleutospores are two-celled and have thick walls and per- 
sistent pedicels. They remain attached to the stubble until the 
following spring and then either one or both cells composing them 
produce an outgrowth known as a promycelium (nothing but a 
basidium divided transversely into four cells). Each cell of the 
basidium is capable of producing a branch, at the tip of which a 
basidiospore is formed. These basidiospores are blown to the 
Barberry (Berberis) and infect the leaves of this plant. The 
mycelium runs in the intercellular air spaces and causes the appear- 
