. Plant studies; an elementary botany. Botany. THALLOPIIYTES: FUNGI 281 wall, and forms wliat is called the "black rust,"which ap- pears late in the summer on wheat stubble. These spores are the resting spores, Avhich last through the winter and germinate in the following spring. They are called Icleuto- spores, meaning the " last spores " of the growing season. They are also called " winter spores," to distinguish them from the urcdospores or " summer ; At first this teleutospore-bearing mycelium was not recognized to bo identical with tlie uredo
. Plant studies; an elementary botany. Botany. THALLOPIIYTES: FUNGI 281 wall, and forms wliat is called the "black rust,"which ap- pears late in the summer on wheat stubble. These spores are the resting spores, Avhich last through the winter and germinate in the following spring. They are called Icleuto- spores, meaning the " last spores " of the growing season. They are also called " winter spores," to distinguish them from the urcdospores or " summer ; At first this teleutospore-bearing mycelium was not recognized to bo identical with tlie uredospore-bearing mycelium, and it was called Purciniu. This name is now retained for the whole polymorjjhous plant, and wheat rust is I'ucclnia grmninis. This mycelium on the wheat, with its summer sjDores and winter spores, is but one stage in the life history of wheat rust. In the spring the teleutospore germinates, each coll developing a small few-celled filament (Fig. 252). From each cell of the filament a little branch arises which develops at its tip a small spore, called a s2io- ridiimi, which means " ; This little filament, which is not a parasite, and which bears sporidia, is a second phase of the wheat rust, really tlie first phase of the growing season. The sporidia are scattered, fall ujion barbeiTy leaves, germinate, and develop a mycelium which spreads through the leaf. This mycelium produces sporophores whicli emerge on the under surface of the leaf in the form of chains of reddish-yellow conidia (Fig. 253). These chains of conidia are closely packed in cup-like receptacles, and these reddish-yellow cup-like masses are often called. Hi. '.'53. Wheat rnst, show- ing;: a teleutospore germina- ting and forming a short fil- ament, from fonr of whose cells a spore branch arises, the lowest one bearing at its tip a sporidinm.—After H. Marshall Please note that these images are extracted from scanned page images that may have been digitally en
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1900
