. Fungous diseases of plants : with chapters on physiology, culture methods and technique . Fungi in agriculture. 238 FUNGOUS DISEASES OF PLANTS. =**% formed within the vessels. These conidia, frequently spoken of as microconidia, are at first cylindrical or elliptical, and with- out septa; but they may become slightly curved and once or twice septate. These are capable of germination and growth within the tissues. On the surface of the host and in culture a type of conidia known as macroconidia may be produced in quantity. These are lunulate or crescent-shaped and from three to five times sep
. Fungous diseases of plants : with chapters on physiology, culture methods and technique . Fungi in agriculture. 238 FUNGOUS DISEASES OF PLANTS. =**% formed within the vessels. These conidia, frequently spoken of as microconidia, are at first cylindrical or elliptical, and with- out septa; but they may become slightly curved and once or twice septate. These are capable of germination and growth within the tissues. On the surface of the host and in culture a type of conidia known as macroconidia may be produced in quantity. These are lunulate or crescent-shaped and from three to five times septate, measuring 30-50 X 4-6 fi (Fig. 99, c). Upon the host the conidio- phores arise in loose stromatic tufts known as sporodochia. In cul- ture all gradations be- tween the small and large conidia may be observed. Moreover, an oidium-like stage is Fig. 100. Perithecia, Ascus, and sometimes produced, Paraphysis of Nkocosmospora and â the race f this b (After Erw. F. Smith) fungus on the melon chlamydospores are not uncommon in old cultures. The ascus stage of the fungus has been found both on the host plant and in cultures upon steamed potato cylinders and other solid media in which ascospores were sown. In the case of the cowpea fungus the line of culture work so accurately followed out (Smith) has shown conclusively that the perithecia may be devel- oped from both types of conidia and that the perithe- cium is undoubtedly a stage in the development of the wilt fungus. As the fungus shows considerable differences on the different hosts in regard to the ability to produce perithecia, so it shows also a difference in the ease or difficulty with which the ascus stage may be produced in artificial cultures from the conid- ial stage. The perithecium of the fungus is superficial, more or less scattered, flask-shaped (Fig. 100), and frequently orange vermilion in color, measuring about 250-350 X 200â300 p. The neck may be straight or slightly curved. The ostiolum is closed until a
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Keywords: ., bookauthorduggarbe, bookcentury1900, bookdecade1900, bookyear1909
