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_ 15. The protruding neck of the ostiolum through which the 
spermatia are discharged. These pycnospores have now no known 
function. They will not germinate and are supposed to be vestigial male 
cells (sperms). : 
Study the aecia and oBSERVE:— 
_. 16. That they are sunken in the tissues; at first covered by 
the: epidermis of the host. Locate one that has not burst through the 
epidermis. The pycnia are more superficial; subepidermal or sub- 
cuticular? 
17. The fine interwoven mycelial threads between the host- 
cells about the aecia. Do they ever penetrate into the host-cells? 
18. That it is from a densely interwoven mat of this mycelium 
that the structures of the aecium are developed; to be seen at its base. 
19. The closely packed club-shaped sporophores in the base 
of the cup, arising from the mycelial mat. 
20. The chains of spores cut off from each sporophore, forming 
the parenchyma-like mass that fills the cup. Why are the immature 
aeciospores angular in outline? Note that the maturing spores at the 
mouth of the aecium become globose. 
21. The large cells forming a lining to the cup,—peridial cells. 
They also arise in chains from short mycelial branches similar to the 
sporophores. Note the difference in the thickness of the wall of the inner 
and outer faces of the cells. This lining of the cup is pseudoparenchyma- 
tous and is called the peridium. 
The mycelium of the aecial stage arises from the one-celled basidiospore, 
and each cell is uninucleate. When the formation of the aecium begins, 
there is a sexual fusion of many pairs of mycelial branches in the region 
of what is to be the base of the cup. From each pair of branches arises 
a single binucleated stalk,—a sporophore of the aecium. .A chain of 
spores are developed from each of these binucleate sporophores by suc- 
cessive conjugate nuclear divisions and a laying-down of a septum between 
the pairs of nuclei thus formed. Examine stained sections carefully under 
high-power and LOcATE:— 
22. The paired nuclei in the sporophores; in the aeciospores. 
Make a DRAWING to show the structure of the aecium, the pycnium 
and their relation to the host-tissues as seen in longisection. 
Remove with a needle or scalpel some mature aeciospores from the 
diseased stalks provided. If dry, mount in potassium hydroxide. Study 
and OBSERVE :— : 
23. The form, size, color, contents and markings on the epispore. 
DRAW several aeciospores. 
But cne crop of aeciospores is produced. With the maturity and 
discharge of the last of them the activities of the primary cycle cease. 
The aeciospores initiate secondary cycles through which alone the patho- 
gene perpetuates itself until the following year. There is no saprogenesis 
in the primary cycle. 
Secondary Cycles develop on the stems, branches and needles of 
stalks affected by the aecial stage and on those of neighboring asparagus 
lants. 
e Pathogenesis. The first secondary cycles are initiated by aecio- 
spores which fall upon the host. These germinate in the dew which 
forms at night and send out each a germtube which rapidly grows along 
