370 THALLOPHYTES 
velvety appearance. These erect hyphae are conidiophores and 
bear conidiospores as shown at B in Figure 320. The conidi- 
ospores are scattered by the wind and upon germination grow 
directly into hyphae which can penetrate a young shoot and start 
Fic. 320.— Black Knot, Plowrightia 
morbosa. A, branch of a Plum, showing the 
wart-like excrescences caused by the Fungus; 
B, conidiophores producing conidiospores 
(x 500), and at the right a conidiospore 
germinating; C, two perithecia sectioned 
lengthwise, showing the asci and paraphysecs 
within (X 50); D, asciand paraphyses more 
highly magnified. 
the disease anew. In late 
summer after the produc- 
tion of conidiospores is 
over, the knot becomes 
black and on its surface 
occur numerous small 
papillae which are the 
flask-shaped _ perithecia, 
opening with a pore and 
lined on the inside with 
ascl as shown at C on 
Figure 820. ‘rhe asco- 
spores are mature and 
ready to be distributed 
early the next spring. 
It follows then that the 
disease may be spread dur- 
ing the early spring by 
ascospores or during late 
spring and summer by the 
conidiospores. The de- 
struction of the knots be- 
fore the shedding of the 
spores will check the dis- 
ease. Bordeaux mixture 
applied at proper times is 
useful in checking the dis- 
ease, but most attention 
should be given to the de- 
struction of the diseased 
branches. 
Ergot (Claviceps purpurea and Paspali).! — Ergot is a parasite 
on the young ovaries of the Grasses, being especially common on 
Rye and occurring sometimes on Wheat, Barley, and a number of 
1 Ergot and Ergotism. Press Bulletin 238, Nebraska Agr. Exp. Sta., 1906. 
Life History and Poisonous Propertics of Claviceps Paspali. Vol. 7, No. 9, 
pp. 401-406, Jour. Agr. Research, U.S. Dept. Agr., 1916. 
