The Major Vegetation of Lake Okoboji

The major vegetation of Lake Okoboji consists chiefly of submersed seed plants. The algae are always in evidence and play an important part in the life of the lake since they are used as food by many lower animals, but with the exception of Chara they are seldom conspicuous and never large

Notes on Heteranthera dubia

One of the common aquatic plants of our Iowa lakes is Heteranthera dubia (Jacq.) MacM. In the lakes of the Okoboji region this form is conspicuous along sheltered shores of suitable depth. While only sparingly present on the more exposed margins of the larger bodies of water it grows luxuriantly in the shallower bays and associated smaller lakes. In waters of appropriate depth considerable areas are often dominated by this form, sometimes to the exclusion of other large plants. During the summer of 1910 many acres of the long slough south of Center Lake were occupied almost exclusively by this species. Portions of the upper end of East Okoboji Lake were occupied this past summer by extensive beds of this plant where for a number of years it had developed but scantily owing to the higher water level. The writer desires in this brief article to call attention to the apparently uniform cleistogamy of this plant in such habitats

Some Wound Responses of Foliage Leaves

The leaves of plants are their most exposed organs. The thin summer foliage of herbaceous plants and deciduous trees generally suffers so severely that one rarely finds an uninjured leaf. While the degree of wounding is less serious in the evergreens, since they are tougher and offer greater resistance, lesions are not uncommon on these especially on the broader leaved evergreens. The plant\u27s ability, therefore, to deal with such frequent accidents must be highly developed to meet these daily needs for renewed cortex

The Dwarf Leaf of Cercis Canadensis

For morphological investigations the selection of material is of primary importance. This is especially significant in the comparative study of leaves since these organs may have marked differences in size and structure on a given branch or on a single twig. During development they are responsive not only to environmental conditions but also to factors operating within the plant. Trees often develop diminutive foliage and insertion of the dwarf leaf on the axis may be very close to others of larger growth. This anisophylly is pronounced in many plagiotropic shoots and may also be associated with basal-apical relations. Such dwarf leaves are common in Cercis Canadensis, especially on secondary branches. This paper takes up the dwarf, palmate leaf of Cercis in comparison with its sun and shade leaves of larger growth. These results are also compared with the findings of Obaton who studied the dwarf, pinnate leaves of several species. (Obaton, F., 1922, Revue Gen. de Bot. Vol. 34). The contrasting expressions in these two types of dwarf leaves are of special interest

The Leaf Organization of Hedera Helix

Hedera helix L. is commonly grown in our area as an indoor ornamental plant and in milder climates it thrives outdoors. Its capacity to endure difficult conditions is well known and quite naturally it has been used extensively in teaching and research. Several studies have related to its leaf form and size under various conditions. Ursprung and Blum explored its osmotic values and their work was later summarized by Ursprung (1929). Watson\u27s recent papers (1942 a., 1942 b) discussed certain, aspects of its leaf tissues. The present paper deals with general foliar organizati9n of this plant in comparison with mesomorphic leaves

On the Significance of the Minor Venation of Foliage Leaves

Experiments with living mesophytic foliage leaves show that the smaller veins are capable of carrying enormously increased overload. There seems to be no structural modification of the minor veins in meeting these increased demands

The Cicatrization of Wounded Citrus Leaves

Since the independent plant must expose green tissues to light, massive opaque coverings may not be employed by foliage leaves. Their exposed position and necessarily delicate structure render them peculiarly liable to injury. The writer has been interested in noting some of the responses of foliage leaves to injuries. A paper now in press summarizes the literature of this subject and describes the healing structures developed by certain mesophytic leaves following wounding

Concerning the Capacity of Foliage Leaves to Withstand Wounding

Foliage leaves are peculiarly liable to injury. From the nature of their work they are denied the protection given to older stems and larger roots. Their delicate structure not only invites insects, larvae, and other plant eating animals, but subjects them to repeated injury by purely mechanical agencies. Observation of leaves as they are found torn and mutilated in nature shows that they possess considerable power of adjustment to wounds and injuries

A Factor in the Distribution of Minor Veins in Dicotyledon Leaves

Critical survey of a wide series of foliage leaves shows a fairly close relation between mesopyll organization and intervascular distance. Among Dicotyledons there is a close correlation between relative amount of leaf tissue that is horizontally arranged in the blade in comparison with that having cells elongated at right angles to the epidermis

A Note on Axis Restoration in a Gymnosperm Tree

Injury to the major axis of a tree with excurrent growth often results in the development of a dwarfed or unsymmetrical crown. In the case of certain gymnosperms the lost apical shoot can be restored by bending upward one of the adjacent lateral branches and fastening it in upright position. In this way it may be induced to develop into a radical, lead shoot and dominate the further growth of the tree. While this practice is fairly well known it should occasionally be brought to the attention of the general public. The following paragraphs record another instance of the successful substitution of a lateral branch for the lost apical shoot of an injured pine tree