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The genus may be subdivided as follows:

Lamina deltoid-ovate or cordate, base auriculate or truncate; rhizome globose, 5-10 mm. thick; commonstalk short, hypogean; fronds two to four, rarely solitary; spike short and stout. (Southern States, Mexico and South America.) 1. O. crotalophoroides Walt.* Lamina lanceolate or spatulate to ovate, rarely broader, base acute, obtuse or rounded.

Plants normally small, usually less than 9 cm. high (1.5-11.5); fronds two or three, rarely solitary; commonstalk hypogean, usually less than the height of the plant.

Rhizome very small, short-cylindric to globose, 2-5 mm. long, 1.8-5 mm.
thick, lamina usually plane and horizontal, - the height of the plant ;
median vein emitting one or two branches, areolae mostly small and
divergent; spores 0.030-0.040 mm. thick. (
(Southern States and Cuba.)
2. O. tenerum Mett.
Rhizome larger, long-cylindric, 2-17 mm. long, 2-3 mm. thick, lamina
usually folded and upwardly inclined, the height of the plant;
median vein simple except for secondary connecting veinlets, areolae
mostly larger and parallel; spores 0.040–0.050 mm. thick. (California
and Mexico.)
3. O. californicum Prantl.
Plants larger, usually more than 12 cm. high (6-40); fronds usually solitary;
commonstalk or more epigean, }–} the height of the plant.
Lamina lanceolate, spatulate, elliptic, oblong or ovate, apex rounded or
sometimes acute, not apiculate; spores reticulately marked with thin
ridges, more or less verrucose.

Plants usually more than 15 cm. high; lamina variable in shape;
commonstalk usually the height of the plant or more, mostly
epigean. (Usually in wet boggy ground, Northeastern North America,
Europe and Asia; also in Mexico?)
4. O. vulgatum L.

Plants mostly less than 15 cm. high; lamina lanceolate or elliptic;
commonstalk about the height of the plant, about hypogean. (In
sand, New Jersey, New York and New Hampshire.)

5. O. arenarium E. G. Britt.

Lamina elliptic or rarely ovate. usually acute, apiculate; spores merely
finely pitted, faintly verrucose. (Virginia and Indiana to Mexico.)
6. O. Engelmanni Prantl.

Prantl, in his monograph, in which he treats the genus from a world-wide point of view, divides what he considers to be Euophioglossum into two groups of species according to the branching or non-branching of the mid-vein of the lamina, one of the characters used here to distinguish O. tenerum from O. californicum. In a general treatment, it may be necessary to make use of this * O. reticulatum L. of tropical regions in general, is like O. crotalophoroides in the shape of the lamina, but differs in its greater size, usually solitary fronds, and in having a long, mostly epigean commonstalk, and a cylindric rhizome.

character, but it is hardly satisfactory even when most distinctive, and is often obscure and hard to ascertain, and, in a consideration of the species of a relatively limited area, its use may well be avoided. In his treatment of the American species, Prantl's work is in some respects deficient, owing to the fact that his material of these plants was for the most part scanty. For example, his description of O. crotalophoroides, a species originally from South Carolina, was with two exceptions based on South American collections. Of O. californicum he saw only part of one collection, of O. tenerum, one specimen, and similarly of others from South America. The result has been that some of his descriptions are rather incomplete, but in view of his insufficient material it is to be wondered that he was able to define the species as accurately as he did, and it is a tribute to his ability that his conception of specific limits has, after study of ample material, been generally affirmed.

NEW YORK BOTANICAL GARDEN,

THE STORY OF THE MANGROVE

BY GEORGE V. NASH

Those who have been to the southern parts of our own state of Florida, or have visited the shores of tropical America, have perhaps noticed, fringing the shores in many places, a shrub or small tree, from the horizontal branches of which descend long gaunt roots, and bearing, usually in great profusion, long clubshaped pendulous bodies which sway and dangle in every breeze. But have you realized the vast importance of this plant and the tremendous work it is accomplishing, and have you really understood what those peculiar long bodies are and what an important part they play in the dispersal of this plant, and hence in the increase of tillable land in the tropics, for this unassuming plant is a great land builder - how I will attempt to show later.

To fully understand what the plant is doing, we must first understand the plant itself. A native of the lowlands of its home, where it is always warm, this plant seems to have no seasonal

activity, but to be always growing, so that flowers and fruit may be found upon it at almost any time. If you will examine the flowers you will find that they have four sepals and petals, and present an appearance not unlike many other flowers with which you are acquainted.. But look further, and you will find hanging to the tree numbers of club-shaped bodies six to eight inches long, or even longer, in the manner shown in the fourth illustration of this article, where in the higher branches these may be

[graphic]

FIG. 1. Showing hypocotyls and mangroves in various stages of development.

clearly seen. It is these odd bodies which are peculiar to the mangrove, and which lend to it its great interest, but what are they? They are really young plants, for the seeds of the mangrove germinate while still in the ovary, the developing embryo finally bursting through the apex of the ovary and producing these long club-shaped bodies, known to botanists as hypocotyls. It is not the hypocotyl which is peculiar to the mangrove, for this is found in all young plants, but it is the great and unusual

development of this organ, while still attached to the tree, which is peculiar. At the small end of these peculiar bodies is the plumule, where are concealed the first leaves of the plant, while the other end of the hypocotyl is much enlarged.

Now what happens when the young plant has reached that stage in its development when it separates from the parent tree? The mangrove, as has been said, grows along the shore, and the pendant hypocotyl, when it breaks from the tree, falls, as would

[graphic]

FIG. 2.

A well-developed colony extending itself into the water. a plummet, the big end down. If the water under the tree be shallow, and even eighteen inches would not thwart its object, these bodies penetrate the mud in an upright position and soon take root, sending forth their leaves and in a short time developing into vigorous plants. If, on the contrary, the water be too deep, they rise to the surface after their plunge and float about, for they are lighter than the water, at the capricious whim of tides and winds. In time some of them find a resting place on

a congenial shore, perhaps after tortuous and devious journeyings, and form the basis of a new colony. This is well shown in the first illustration, where a number of these plants may be seen in the hypocotyl stage. To the left is a young one firmly attached to the soil and beginning to grow, while in other parts of the picture will be found other plants in various stages of development. This colony increases until a condition represented in the second picture is reached. Here we see the network of roots,

[graphic]

FIG. 3. Interior of a mangrove swamp, showing interlacing roots.

to which reference will again be made, and also the long gaunt roots descending from the spreading branches. It is these descending roots which extend the zone of the mangrove further and further into the water. Imagine this process to have continued for a number of years, then let us enter one of these mangrove swamps, and we would see before us a vast tangle of arching and interlacing roots, as represented in the third illustration, the surface of this entangled mass being two to three or

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