A SERIOUS LETTUCE DISEASE. 
101 
in the hypha. In the younger growing tips the septa are very far 
apart, and become closer in the older parts. There is no completely 
regular method of hyphal branching, although the greater number of 
•. I J ,7.-.- 
Fig. 11. —Mycelial thread showing three stages in its development; a , young; b, medium; c, old. 
branches seems to arise as perpendicular outgrowths near the end or 
middle of a cell, Fig. 8. There are tw r o other methods of branching, 
one of which will be discussed under “attachments.” The other is 
that in the case of a young hypha, which is growing rapidly and has 
an abundance of nourishment, in which case three or more branches 
arise, frequently simultaneously, and the main hypha loses its pre¬ 
dominance ; the three branches being equally vigorous. At first, 
2 
