_Conductive System._—Sieve tissue, tracheary tissue, milk tissue, conducting parenchyma, etc. _Food-storing System._—Water reservoir, water tissue, slime tissue, fleshy roots and stems, endosperm and cotyledons, etc. _Aerating System._—Air spaces and tubes, special air tissue, air-seeking roots, stomates, lenticels, etc. _Secretory and Excretory System._—Water glands, digestive glands, resin glands, nectaries, tannin, pitch and oil receptacles, etc. _Apparatus and Tissues for Special Duties._ Holdfasts. Tissues of movement, parachute hairs, floating tissue, hygroscopic tissue, living tissue. For perceiving stimuli. For conducting stimuli, etc. FOOTNOTES: [37] =Suggestions to the teacher.=—In the study of the flowering plants in the secondary school and in elementary courses three general topics are suggested. 1st, the study of the form and members of the plant and their arrangement, as in Chapters XXXVIII-XLV. 2d, the study of a few plants representative of the more important families, in order that the members of the plant, as studied under the first topic, may be seen in correlation with the plant as a whole in a number of different types. 3d, the study of plants in their relation to environment, as in Chapter XLVI. The first and second topics can be conducted consecutively in the classroom and laboratory. The third topic can be studied at opportune times during the progress of topics 1 and 2. For example, while studying topic 1 excursions can be made to study winter conditions of buds, shoots, etc., if in winter period, or the relations of leaves, etc., to environment, if in the growing period. While studying topic 2 excursions can be made to study flower relations, and also vegetation relations to environment (see Chapters XLVI-LVII of the author’s “College Text-book of Botany”). It is believed that a study of these three general topics is of much more value to the beginning student than the ordinary plant analysis and determination of species. [38] It is interesting to note that in some foliage shoots the stem is entirely subterranean. See discussion of the bracken fern and sensitive fern in Chapter XXXIX. [39] Some fibers occur also very frequently in the Fundamental System, forming bundle-sheaths, or strands of mechanical tissue in the cortex. CHAPTER XXXIX. THE DIFFERENT TYPES OF STEMS. WINTER SHOOTS AND BUDS. I. Erect Stems.