144 
ment ceases and the black resting-spores of the pathogene predominate. 
Examine the old diseased branches and needles provided and OBSERVE :— 
8. The crowded black sori or telia. How do they compare 
with the uredinia as to prominence, shape, size, arrangement on the stems 
and branches, and dustiness of their spore-masses? 
9. That the host-tissues covered with the telia are dead and 
shriveled. This is the last: phase of the disease, the autumn or winter 
condition of rusted plants. 
Make a DRAWING of a diseased stem, and also of the pustules as seen 
under the hand-lens. 
ETIOLOGY 
The asparagus rust is caused by Puccinia Asparagi DeCandolle, a 
species of the Uredinales, an order of fungi, the members of which are the 
most highly specialized of the Basidiomycetes. It is an autoecious patho- 
gene producing its different spore-forms all upon the same host. 2 
Life-history. It produces during its life-cycles all the known fruiting 
structures of the rusts: pycnia (O), aecia (I), uredinia (II), telia (III), 
and basidia (IV), each with their characteristic spores. It is therefore said 
to be a Eupuccinia, that is, a true Puccinia. (See McAlpine, ‘Rusts of 
Australia, p. 10-11.) . 
The Primary Cycles have their development early in the spring on 
the young shoots before Jufy first; often as early as March but usually 
during April and May, depending upon the locality and season. Pycnia 
and aecia only are developed during the primary cycles. 
Pathogenesis. The inoculum for the primary infections. consists 
of the basidiospores or sporidia produced on the promycelium from the 
overwintered teliospores on diseased stalks and needles. Examine the 
germinated teliospores on slides provided; or study California Bul. 165, 
fig. 27. OBSERVE :— 
10. The long slender promycelium (basidium) put forth from 
each cell of the teliospore; 4-celled near the apex. 
11. The long pointed sterigma from each basidial cell, bearing 
at its apex a thin-walled ovoidal.basidiospore. Each spore contains one 
nucleus and finely granular protoplasm. 
DRAW or COPY to show sporidia ready for dissemination. 
These sporidia are carried by the wind or splashing rain to nearby 
shoots just coming up. There in the moisture on the surface they send 
forth a germtube which penetrates the tender epidermis and gives rise to 
a locally spreading mycelium. From the mycelium, within less than a 
month, are produced first pycnia and promptly after them, aecia. 
Study cross-sections of the stalk (freehand or prepared) through an 
aecial lesion; or California Bul. 165, fig. 18. oOBSERVE:— 
12. The large cup-like aecia and scattered among them the 
minute flask-shaped pycnia (spermogonia). 
Locate a pycnium and study its structure under the high-power. MAKE 
OUT :-— 
ai 13. The very slender interwoven mycelium forming the pycnial 
w 
14. The long slender sporophores arising from the wall-mycelium 
and converging at the center of the pycnium about a small cavity which 
is filled with the very minute bacterium-like pycnospores (spermatia). 
