Nature and development of plants . y infested withrust. For this reason, a law was passed early in the history of[Massachusetts compelling the destruction of the barberry suggestion of relationship between the cluster-cup stage ofthe barberry and the rust of the wheat finally led to the inocu-lation of wheat plants with aecidiospores and this resulted aftera week or more in the appearance of the characteristic rustystreaks on the leaves of the wheat. Considerable variation characterizes these rusts, not all of themhaving so elaborate a life history as that outlined above. Oneof the
Nature and development of plants . y infested withrust. For this reason, a law was passed early in the history of[Massachusetts compelling the destruction of the barberry suggestion of relationship between the cluster-cup stage ofthe barberry and the rust of the wheat finally led to the inocu-lation of wheat plants with aecidiospores and this resulted aftera week or more in the appearance of the characteristic rustystreaks on the leaves of the wheat. Considerable variation characterizes these rusts, not all of themhaving so elaborate a life history as that outlined above. Oneof the most common species of Puccinia affecting the wheat isperennial in the wheat and possibly in other grasses where itproduces uredospores in the spring, thus, the aecial, telial andbasidial stages are eliminated. In the apple rust, the uredinalstage is missing. This disease produces on the leaves of variousmembers of the apple family, yellow patches in which are formedtube-like cluster cups (Fig. 162, A). The aecidiospores are only. Fig. 162. A rust, Gymnosporangium, that infests the juniper and mem-bers of the apple family: A, cluster cups on leaf of thorn apple. B,teleutospore stage on red cedar, juniper. capable of infesting the juniper, on the branches of which theyproduce gall-like swellings (Fig. 162, B) known as cedar apples16 226 AN ALLY OF THE RUSTS and also bushy outgrowths known as witches brooms. In thespring, tubular masses of hyphae bearing numerous teleuto-spores radiate out from these galls and in the early spring rainsthese strands swell up, forming conspicuous yellow, jelly-likemasses. The basidiospores are developed in the jelly and infestthe leaves of the apple, thorn, shadbush, etc. In some of thegenera of rusts all the stages appear upon the same plant as inthe May apple and jack-in-the-pulpit. In the early spring thestems and leaves may often be seen infected with the yellowcluster cups which are followed later by the dark-colored teleuto-spores. In other
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