. Botany for agricultural students . Botany. 192 STEMS Closed vascular bundles and their scattered arrangement are the chief distinguishing features of the anatomy of monocotyle- donous stems. Structure of Herbaceous Dicotyledonous Stems Herbaceous Dicotyledons constitute an important group, for they include many forage plants, notably the Clovers and Alfalfa, some important fiber plants as Flax and Hemp, most vegetables, and many greenhouse plants. In the tropical countries there are a few Gymnosperms that are herbaceous, but in general features their anatomy is quite similar to that of herba
. Botany for agricultural students . Botany. 192 STEMS Closed vascular bundles and their scattered arrangement are the chief distinguishing features of the anatomy of monocotyle- donous stems. Structure of Herbaceous Dicotyledonous Stems Herbaceous Dicotyledons constitute an important group, for they include many forage plants, notably the Clovers and Alfalfa, some important fiber plants as Flax and Hemp, most vegetables, and many greenhouse plants. In the tropical countries there are a few Gymnosperms that are herbaceous, but in general features their anatomy is quite similar to that of herbaceous Dicotyledons. All stems of the herba- ceous dicotyledonous type, whether they are stems strictly herbaceous through- out or only the young branches of woody stems, have pith, vascular cylinder, and cortex which occupy well separated regions when well Fig. 171. - Diagram of a cross section developed. Cross sections of a well developed herbaceous stem, show- appear to the naked eye ing the epidermis (a); band of tissue (&) about as shown in Figure composed of cortex and phloem; xylem ^7; The epidermis, cortex, cylinder (c); and pith {d). ^^^ pj^j^^^^ ^^^^ ^^^ ^^^^ outer zone, while the xylem forms the woody cylinder just within the soft zone, and encloses the pith, which occupies the center of the stem. In order to trace the development and study the anatomy of the different tissues, we must turn to highly mag- nified sections as shown in Figure 172. The Cortex, which is the larger part of the outer zone of tissues, is covered by the epidermis, and includes the starch sheath as its innermost layer. Just under the epidermis some of the cells of the cortex are transformed into collenchyma cells, which are par- ticularly abundant in the angles of the stem shown in the Figure but more generally distributed around the stem in many other plants. The collenchyma cells, often noticeable in sections on account of their whitish glistening appearance, have much thick-. Please note
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
