Nature and development of plants . tes. They exhibit a degree ofvariation not paralleled among other plants; as many as fivedifferent kinds of spores being formed by some species in theirlife history. This is due, doubtless, to the influence of the cli-mate, the spores varying with the season (spring, summer andfall) and the plants upon which the fungus grows may be acontributing factor to the variation, for one and the same fungusmay grow upon different plants, producing one or more kindsof spores on each. (a) The Life History of Puccinia.—Several species of thisgenus infest wheat and illustr
Nature and development of plants . tes. They exhibit a degree ofvariation not paralleled among other plants; as many as fivedifferent kinds of spores being formed by some species in theirlife history. This is due, doubtless, to the influence of the cli-mate, the spores varying with the season (spring, summer andfall) and the plants upon which the fungus grows may be acontributing factor to the variation, for one and the same fungusmay grow upon different plants, producing one or more kindsof spores on each. (a) The Life History of Puccinia.—Several species of thisgenus infest wheat and illustrate the many forms that may ap- 222 LIFE HIST< )RY OF A RUST pear in the life history of a rust. One phase of the life of thisparasite appears upon the leaves of the barberry. During Mayand June the mycelium growing in the leaves forms roundishbodies which rupture the epidermis and finally open out intocups filled with chains of yellowish spores. An examination ofFig. 159 shows that these spores are found at the end of hyphac. Fig. 159. Cluster cups as seen in section of leaf of spring beauty, Clay-tonia. At right one of the cups is ruptured, exposing the a small cup, pycnidium, is discharging pycnidiospores that are pos-sibly functionless male gametes. as in the powdery mildews and surrounded by a layer of ratherthick-walled hyphae. This stage of the rust is known as thecluster cup or aecial stage and the spores are called smaller spore-bearing cups, known as pycnidia (sing, pyc-nidium), are associated with this, phase of the fungus. Thesesmall spores, while capable of germinating, do not appear toenter into the life history of the fungus by producing a new para-site. They have been looked upon as male gametes that origi-nally effected fertilization in a female organ from which de-veloped the spore-hearing cluster cup, the process being similarto that noted in the Red Algae where fertilization resulted inthe formation of a spore co
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