. Bulletin. Plant diseases -- United States. 19 myct'liiil-liko stnictiuc hclicvod to be left by the aphis wtis always presiMit, extending" from the surfaee of the leaf down to the soft bast of the vascular bundle, and often l)eyond into the central niesophyll por- tions of the leaf (tij^s. 2 and o, and PI. 11, lig. 4). Large numbers of cultures were also made from spots known to be produced by aphides, but with the same negative results as before described. Similar experiments with thrips showed conclusively that they are the cause of the elongated spots (tig. -4, and Pis. 1 and 111) and
. Bulletin. Plant diseases -- United States. 19 myct'liiil-liko stnictiuc hclicvod to be left by the aphis wtis always presiMit, extending" from the surfaee of the leaf down to the soft bast of the vascular bundle, and often l)eyond into the central niesophyll por- tions of the leaf (tij^s. 2 and o, and PI. 11, lig. 4). Large numbers of cultures were also made from spots known to be produced by aphides, but with the same negative results as before described. Similar experiments with thrips showed conclusively that they are the cause of the elongated spots (tig. -4, and Pis. 1 and 111) and the dis- tortion of the foliage, and it was also found that the red spiders work- ing on the immature leaves produced the very minute spots by sucking th(» nourishment from the epidermal cells and those immediately Fig. 4.—Cross section through a fully developed spot produced by thrips. The epidermal cells have collapsed and the underlying palisade parenchymal cells are somewhat elongated and have lost most of their chloroplasts. (Drawn with Zeiss camera lucida, x 282 diameters.) It was thought desirable to get more accurate information in regard to the manner in which aphides obtain their nourishment from the tissues, and for this purpose leaves upon which they had been col- onized .were carefully cut from the plant while their sucking apparatus was still inserted in the tissues. These leaves were dropped into 75 per cent alcohol saturated with corrosive sublimate, and many of the aphides were thus killed before they had time to withdraw their beaks or punc- turing bristles. Portions of the leaf with the beaks attached were then cut out, carefully dehydrated, and infiltrated with parafiin, the sections being then cut and mounted in series, and thus preparations showing the puncturing apps^-^+us in place in the tissues obtained (fig. 5, and PL II, figs. 2 and 3^. Tbe-puncturing bristles always. Please note that these images are extracted from scanned page image
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Keywords: ., book, bookcentury1800, bookdecade1890, bookpublisherwashingtongpo
