. Carnegie Institution of Washington publication. THE OLDER SPOROPHVTE 173 of procambial cells. This is the single axial stele or commissural strand which had not yet begun to develop in the plant with five leaves. The older leaf base, shown in this section, has a single large vascular bundle, crescent-shaped in outline and con- centric in structure, and there are also seen the two small concentric bundles belong- ing to the stipules. All the leaf traces in the older leaves are concentric in structure, with well- developed internal phloem, and thus differ from the collateral traces of the earl
. Carnegie Institution of Washington publication. THE OLDER SPOROPHVTE 173 of procambial cells. This is the single axial stele or commissural strand which had not yet begun to develop in the plant with five leaves. The older leaf base, shown in this section, has a single large vascular bundle, crescent-shaped in outline and con- centric in structure, and there are also seen the two small concentric bundles belong- ing to the stipules. All the leaf traces in the older leaves are concentric in structure, with well- developed internal phloem, and thus differ from the collateral traces of the earliest leaves. This concentric structure of the bundle is already well marked in the fourth leaf, where, however, the protophloem is mainly developed upon the outer side. F shows the arrangement of the bundles in a section somewhat further down. The two strands from the oldest of the three leaves seen in the apex have joined the horns of the crescentic central bundle, which still shows clearly its dual nature. In the younger of the two portions of these sections the first tracheids have just appeared near the free end, while in the older half a line of tracheids extends nearly through the whole of the center. The mucilage ducts at this level are much larger and their cells have become confluent. Close to the large mucilage canal can be seen the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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Keywords: ., bookauthorcarnegie, bookcentury1900, bookdecade1910, bookyear1911
