634 THE SMALLER FUNGI. 
insinuating themselves between the cells that constitute the 
pulp, derive their nutriment at the expense of the growing 
foliage. It is after the pustules assume the white color, and 
are visible on the skin or cuticle, that the reproductive parts 
termed conidia, can be detected. Indeed the whole inte- 
rior of the white pustules is made up of bundles of club- 
shaped tubes, which have been extended from the system of 
` threads, and which tubes give off bead-like strings of cells, 
each bead by turns parting from the chain or necklace, and 
escaping into the air through the distended and ruptured 
pustule. From the multitude of these beads or spores, 
forming a white powdery dust, the term “conidia” is ap- 
plied, which means dust-like. Other plants beside are 
similarly affected, and the water-cress, pepper-grass, mus- 
tard, radish, shepherd’s-purse, and even the purslane, fall 
victims to its ravages. That so hardy a weed as the shep- 
herd’s-purse ( Capsella bursa pastoris) should become pallid 
and sick, indicates the nature of the drain which is made on 
its juices by-this parasite, and it is not improbable that the 
“clubbing” of the cabbage, where the stalk becomes gouty 
and swollen, and. refuses to make a healthy growth, may be 
owing to similar exciting causes in the presence of the my- 
celium of some fungus in its tissues. From the researches 
of M. Provost, in 1807, we learn that the germination of 
the conidia, or spores, is one of the most curious phenomena 
of plant life, and indicates in this low order of vegetation, 4 
relation to higher structural forms, not only in plants but 
even in animals, Thus, if a few particles of the white dust 
is thoroughly immersed in a drop of water, and examined 
under the microscope, “they will rapidly absorb the water 
and swell; soon afterwards a large and obtuse papilla, re- 
sembling the neck of a bottle, is produced at one end of the 
extremities. At first vacuoles* are formed in the contents 
of each conidium (spore). As these disappear, the whole 
granular substance filling the conidium becomes separ?” 
*Vacuole, a little vacunm, or seeming empty space. 

