454 BULLETIN OF THE BUSSEY INSTITUTION. 
EXPLANATION OF PLATES. 
PuaTte I. 
Fumago salicina, Tul., on olive leaves, magnified 600 diam. 
1. Stylospores. 
2. Mycelium on scale of leaf. 
3. a, pycnidia; c, conidia. 
Puate II. - 
. Peronospora viticola, B. and C., conidia magnified 600 diam. 
. Tip of branch more highly magnified. 
Haustoria in stem of Vitis cordifolia. 
. Conidia of Peronospora nivea, Unger, from leaf of Geranium maculatum, 
. Conidia of Peronospora effusa, Grey., from leaf of Plantago major. 
. Conidial spore germinating. 
D> oP co bo 
Pirate III. 
1. Odspore of Peronospora effusa, Grev., from leaf of Plantago major, mag- 
nified 750 diam. 
2. Oodspore of Peronospora viticola, from Vitis zstivalis. 
3, 4, 5, 6, 7, 8. Different stages of development of the zodspores of P. viti- 
cola; 8 is drawn on a larger scale than 6 and 7. 
Pirate IY. 
1. Spheria morbosa, Schw., black knot on cultivated plum. May. Natural 
size. 
2 and 38. Sections of young knot from a choke cherry. Natural size. 
Puiatse V. 
1. Spheria morbosa on cultivated plum. Autumn. Natural size. 
2. Section of knot on choke cherry in May, magnified 690 diam. a, myce- 
lium; 0, conidia. 
3. Conidia more highly magnified. 
4. Section through one side of cavity containing stylospores. From mazzard 
cherry. 
5. Stylospores more highly magnified. 
PuaTE VI. 
1. Section of choke cherry stem, showing mycelium before it has come to 
the surface, magnified 600 diam. 
2. Spermagonia. 
8. Asci and spores of Spheria morbosa from choke cherry. 
4. Perithecium with asci. 
4, 5. Ripe ascospores. 
§, 7. Ascospores germinating. 
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