CHAPTER IV. 
AECIDIOSPORES, 
THE mycelium originated in the tissues of the host-plant 
by the entrance of the germ-tube from a promycelial spore, 
after it has produced a certain number of spermogonia, 
proceeds in the course of its development to give rise to 
the zcidiospores, This spore-form is of considerable 
interest, not only on account of the manner in which it 
arises, but also by reason of its attractive appearance in 
the mature state. The first appearance of the zcidiospores 
consists in the formation of the receptacle (pseudoperidium) 
in which they are contained. The mycelium destined to 
give rise to an zecidium becomes more frequently branched 
and interwoven. At certain points, not immediately 
beneath the epidermis, but pretty deeply placed in the 
parenchyma of the plant, the mycelial hyphz compact 
themselves into spherical bodies, which at first are not 
larger than the parenchymatous cells of the host-plant, The 
bodies (the primordia of De Bary) gradually increase in 
size by the addition of fresh hyphe from the mycelium, It 
can soon be observed that the interior and bulk of these 
bodies consist of a cellular structure, and that they bear 
the greatest possible resemblance to perithecia (Plate IT. 
Fig. 1). They are globose, but rather flattened upon their 
upper surface—that is, the surface nearest to the epidermis. 
