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SECTION OF VEGETABLE PATHOLOGY. oTT 
. (Fig. 3,6). Thisisthe female cell, the protoplasmic contents of which 
are fertilized by the commingling with them of the contents of the 
upper cell of the slender filament which is usually applied to the 
‘upper end of the female cell. The upper cell of the male organ 
contains a substance which corresponds in function to that within 
the cell coat of a pollen grain, while the female cell answers to the 
erm cell within the embryo sac of a young ovule. The process of 
ertilization in the gooseberry mildew is essentially the same as 
that with any ovule among flowering plants, but stripped of all the 
appliances seen in intricate blossoms, and therefore reduced to the 
simplest terms. The rapid propagation of a flowering plant by run- 
ners, suckers, bulbets, or by one or more of a long list of non-sexual 
methods, may be considered as homologous with the vegetative pro- 
cess in the mildews, including the production of the conidial spores. 
The latter are formed by a slow process of budding. As the result 
of fertilization in the young ovule there arises the seed and whatever 
- Inay surround the seed or seeds, namely, the fruit. In the same 
manner the product of fertilization in the mildew under considera- 
tion is a “fruit” which includes the spores and their surroundings. 
The first evident result of fertilization in the mildew is the outward 
and upward growth of numerous short filaments from the base of 
the female cell. These threads soon completely surround the ferti- 
lized cell within and become divided by cross-walls, so that the young 
forming perithecium or spore case assumes the form and appearance 
shown in Fig. 4, Plate XI. If a section should be made through 
the middle of one of these nearly spherical bodies the view would 
show the outside cell situated upon a short stalk and occupying the 
center of the sphere. Later on in the development of the perithecia 
the outer coat becomes thicker by increase in number and size of the 
cells composing it, and assumes a dark chestnut color. At the same 
time some of the surface cells produce slender outgrowths which be- 
come as long as the diameter of the perithecium, and serve to hold 
it in place among the vegetative filaments of the mildew upon the 
surface of the infested host. 
The perithecium at this stage is shown in Fig. 5, Plate XI. While 
these changes have been going on exteriorly the central protoplasmic 
contents have been shaping themselves into eight small masses, around 
which was formed a thick, colorless cell wall, called the spore sac or 
ascus. In Fig. 6 is shown a mature perithecium, the dark thick 
wall of which has been broken open by pressure, and the ascus is 
escaping from within, An ascus is shown in Fig. 7 more highly 
magnified and free from the perithecium. 
On account of the prevailing chestnut color of the ripe perithecia 
the older portions of the mildew lose their white appearance and be- 
come of a dirty brown color. It is therefore easy to determine the 
condition of the mildew from the general appearance of the infested 
spot. Thethick wall of the perithecium is for protection, and the 
spores within do not germinate until after a period of rest, during 
which time the surrounding covering becomes decayed or the spores 
escape by a rupture of its walls. The mildew passes the winter in 
the ascosporous condition, just as many of ourannuals, like corn, etc., 
have their vitality concentrated within the seeds or grains that were 
formed by the mother plant in autumn. These winter or sexual 
spores find their way to the young, moist surfaces of the growing host 
plant during the following spring or summer, and these germinate 
and begin a new mildew spot. 
