65 
of warm weather, the apothecia are developed on these overwintered 
lesions. It has been held by some that from the lesions on fallen leaves 
which have laid on the ground over winter, apothecia are produced which 
supply the primary inoculum. 
Crush a mature apothecium (one that is open) from leaves provided, 
tease well apart, cover and stupy:— 
7. The mature ascospores in the ascus; their shape, structure, 
color, and number in the ascus. DRAW. 
These spores constitute the primary inoculum. If germinating asco- 
spores are available, study and sKETCH. 
The germtube penetrates the upper epidermis of the leaf, and produces a 
locally spreading mycelium with a resulting spot or lesion. At the center 
of this is shortly developed an apothecium without any intermediate 
production of asexual spores as is usually the case among the ascomycetes. 
Make freehand sections of the leaves through the spots, stain with 
methyl blue, wash, and examine with the high-power of your microscope. 
OBSERVE :— 
8. The brown host-cells; the character of their contents; 
the relation of the mycelium to these cells, inter- or intracellular? 
9. How far the mycelium extends. What causes the yellowing 
around the brown cells? 
10. The blue-stained structure on one side of the brown-spot,— 
the apothecium. On which surface does it occur? How deep into the 
leaf does it extend? How does it become exposed? 
ll. That the lower part of the apothecium,—the stroma, is 
composed of small cells. 
12. That arising from the stroma is the hymenium. Of what 
is it composed? (It may be easier to observe the structure of the hymenium 
by crushing a few of the older spots in a drop of water.) 
13. Within the asci, the oval ascospores; how many’ Note 
the oil-drops or guttulae at eachend. These spores are shot from the asci 
during moist conditions, thus disseminating the pathogene. 
Make prawincs, (a) to show the relation of the mycelium to the host- 
cells, its extent and the apothecium; (b) an enlarged view of the hymenium 
to show its structure, the spores and their arrangement in the ascus. 
Saprogenesis. There is some evidence that apothecia may be 
formed on spots which were immature when the leaves fell to the ground. 
This, together with the fact that apothecia may be produced im artificial 
culture media, indicates that apothecial development may in some cases 
result in nature from saprophytic activity. Since, however, mature 
ascospores in apothecia on living leaves are always common and abundant, 
saprogenesis, as such, is an unimportant if not uncommon phase of the life- 
cycle. 
Secondary cycles. These are initiated by ascospores from the 
apothecia produced during the primary cycle, and the pathogene repeats 
in all details the structures and activities of the primary cycle. 
REPORT 
1. Explain the effects of this fungus on the leaf and on the yield. 
2. Show graphically the life-history of Pseudopeziza Medicagints 
(Lib.) Sacc. 
