OBSERVATIONS ON SOME AMERICAN FORMS OF CHARA CORONATA.

BY T. F. ALLEN, M.D.

Chara coronata Ziz. (in ed. 1814), revised by A. Braun to include all known varieties, belongs to the second division of the genus Chara, namely Haplostephane (stipules composed of a simple series of cells); it has but one stipular cell at the base of each leaf, is not corticated, is monoecious and is described as follows in Braun's Characeæ Africanæ: "Plant annual, smooth and flexible. Leaves verticillate nine to eleven, with 4-6 articulations, 3-5 elongated segments and a short mucroniform ultimate segment. Bracts developed at every node; at the terminal node forming with the terminal segment a 3-5 divided crownlet (coronula); the posterior bracts shorter, depauperate or wholly wanting; the anterior about equaling the sporangium, rarely longer, often shorter. Stipules about the size of the leaves. Antheridia and Sporangia produced on the same node, rarely double or triple. Nucleus of the sporangium black, with a calcareous shell and with 7-12 conspicuous striæ on a side."

The European form of this species, known as var. Braunii, has been considered the normal form, occupying as it does an intermediate position in respect to size, development of bracts, size of nucleus and form of the coronula. The nucleus varies from 420 to 550 (micro-millemeters, mille-millemeters) in length, is 9-striate; coronula of the sporangium is short and obtuse; the bracts anteriorly are equal to or shorter than the sporangium, posteriorly they are undeveloped. This form is found also in America, but the more distinctively American form has been known as var. Schweinitzii A. Br. This is usually characterized by a larger nucleus, 550 to 650 ., and by the great development of the bracts, which are often several times longer than the sporangium and are completely developed around the leaf, verticil late, though the posterior are much shorter than the anterior. An African form, var. Perrottetii A. Br., has a large nucleus, 600-650 ., with unilateral bracts equaling in length the sporangium; this form we find in America also. From India, var. Coromandelina A. Br., has been designated by a very large nucleus 600-750 ., with verticillate bracts, nucleus with seven strong angles; some of our forms approach very closely to this,

having verticillate bracts and an equally large nucleus. In the Sandwich islands is found a delicate form in which the cells of the coronula are much elongated, and approaching this form is one collected in New Mexico by Wright. Besides the more distinct forms are many intermediate forms, difficult to place, possessing characters belonging to two or more varieties; indeed the forms of this species from different places are quite numerous. We find the plant everywhere from Canada to Mexico and from Massachusetts to California.

One interesting fact is, that the plant in any given locality is constant in its peculiarities, and though thousands of plants be examined they will all be found to exhibit precisely the same character. This is true not only of this species but of most other species of Characeæ; thus in a pond filled with Chara fætida A. Br., with long bracts and long terminal naked nodes (Macroptila, Macroteles) all the plants will have the same peculiarity and will keep it unchanged year after year, while a neighboring pond perhaps only a few rods distant, may be inhabited by another distinct but persistent form.

A. Braun relates that Chara gymnopus var. Humboldtii A. Br., collected by Gollmer in the same lake in which fifty-five years before Humboldt had gathered it, presented precisely the same characters. We have, however, noticed in one instance an apparent difference in a form of C. coronata collected in precisely the same locality in which it had been found twenty years before, but there might have been a difference in the maturity of the plants. This permanence of slight peculiarities may be owing to the disagreeable odor and taste of the plant, which has often a strong smell of sulphuretted hydrogen, rendering it offensive to animals who might otherwise feed upon it and carry the seeds to other localities; and as the plants grow wholly under water, the seeds are not liable to be carried by the wind. Hybridization seems, therefore, to be infrequent and exceptional. These very qualities, which serve to limit the spread of the Characeæ, may also have determined the persistence of very ancient forms and limited their multiplication.

The characters relied upon for distinctions betweeen varieties, have been the development of the bracts, the size and striation of the nucleus, and the character of the coronula of the sporangium. The general aspect of the plant, size and length of stem, density

or laxity of growth, seems to vary greatly from differences in the character of the water, exposure, et cetera. The plant has been thought to be free from incrustation, but one form from Canada (Pacific Railway survey) is so completely incrusted that it is extremely brittle, and when dry has a gray color; while another form has a most peculiar zonular incrustation, giving the plant a variegated appearance.

The development of bracts seems to be most capricious; though the comparative length of bracts and sporangia seems to be pretty constant in any one locality, the posterior development varies in a single plant, and at times on a single leaf, one node exhibiting verticillate bracts while the next node has absolutely no bracts on its dorsal aspect: this we often find to be the case in the longest bracted forms (var. Schweinitzii).

In America we have every length of anterior bracts from two to three times the length of the sporangium, a little longer, of equal length, a little shorter, to very short bracts, one-half or even a third its length. Some of the shortest bracted forms are found with the largest sporangia and with verticillate bracts.

Size of nucleus.-The smallest, mature nucleus we have yet met with occurs in the form collected by Wright in New Mexico, and determined by A. Braun as var. Braunii forma tenera; it is 420. long and has seven striæ; next in order is the Silver-city form, recently found, 500 . with only five striæ; one from California is 500 . long with seven striæ; from Saranac lake, Vermont, N. Carolina, etc., are forms 520 to 550 . long with longer or shorter bracts; then come the more common long-bracted forms (var. Schweinitzi) with nucleus 550 to 650 . long with 8 to 9 striæ; then some forms with larger nucleus and very short bracts, Penn. and Kansas, 660 to 780 (!) long with 9 to 10 striæ. Both the smallest and largest nuclei now known to us have been associated with short bracts.

The number of stria on the nucleus, representing the whorls of enveloping cells, varies considerably; while in a general way they are more numerous on the longest nuclei, yet a smaller nucleus may have more than one somewhat larger; the delicate Saranac form has 9 striæ, while the larger Vermont form has only 7 (the same as the delicate Braunii-tenera) though the nucleus is larger. The Silver-city form with a nucleus 500 μ. long has 5 striæ, while Braunii-tenera nucleus 420 . has 7 striæ.

The cells of the coronula vary greatly from the closely-set short cells of the more common forms to the divergent and elongated cells of Brauni-tenera, which exhibits an approach to the Sandwich island form (var. Oahuensis A. Br.).

These varying characters with their numerous combinations seem to us to render a division of the species into definite varieties well nigh impossible. As it has now become unadvisable to bestow distinctive names upon the numerous forms of that truly polymorphic species C. fatida A. Br., so in view of the now numerous and rapidly multiplying forms of C. coronata, it seems to us proper to describe them as forms peculiar in many cases to certain localities.

The variations of this plant may be tabulated as follows, giving prominence to the size of the nucleus and length of the bracts, allowing also for variations in the habit of growth, et

cetera:

I. Microcarpa, nucleus less than 500 μ. in length.

1. Macroptila, bracts longer than the sporangia, verticillate or unilateral.

a. Condensata, verticils approximate, the leaves longer than the internodes.

b. Laxior, leaves loose, spreading.

c. Clausa, leaves compact, incurved.

A. Pachygyra, nucleus with thick prominent angles.

B. Leiopyrena, nucleus smooth, or with but slightly prominent angles.

2. Microptila, bracts shorter than the sporangium, verticillate or unilateral.

a. Condensata.

b. Laxior.

c. Clausa.

A. Pachygyra.

B. Leiopyrena.

3. Meioptila, bracts equaling the sporangium in length.

II. Macrocarpa, nucleus more than 600 μ. in length.

1. Macroptila, microptila or meioptila.

A. Pachygyra or Leiopyrena.

a. Condensata, laxior or clausa.

III. Meiocarpa, nucleus of medium size, between 500 and 600 μ. long,

Variations as above.

The American forms may be arranged and designated as follows, beginning with those having the smallest nucleus:

1. Forma tenuior, microcarpa, microptila, unilateralia, laxior, Oxygyra (var. Braunii tenera A. Br.). This form was collected

by Wright in New Mexico (No. 908). It is a slender diffuse

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plant, with rather long leaves. of 5-6 articulations, including the terminal one. The stipules and bracts are very slender; the bracts are unilateral, 'shorter than the sporangium, the anterior rather longer than the lateral. The coronula of the sporangium consists of five cells with elongated divergFIG. 1. Variety Braunii tenera. ing tips, intermediate in aspect between var. Braunii and var. Oahuensis A. Br. The sporangia and antheridia are usually duplicated on each of the two lower nodes. The terminal segment consists of three slender elongated cells forming a tuft. The nucleus is oval with about seven sharp angles, 420 to 460 μ. long and about 250 μ. broad. In the adjoining cut represents the anterior aspect of a node with two sporangia but with the antheridia removed, as at 3. 2 is a terminal node-all magnified forty diameters.

II. Forma microcarpa, microptila, unilateralia, laxior (var. Brauni genuina). This form has been collected near St. Louis by Dr. Engelmann (to whose kindness I am indebted for specimens). Plants diffuse, leaves longer than the internodes, 4-5 articulations, of which the lowest or the two lowest are fertile; stipules rather stout but short; bracts stout, unilateral, much shorter than the sporangium. Coronula of five connivent, blunt cells. Nucleus broadly oval, 475 to 500 . long, with about six ribs, which are blunt and not prominent. The accompanying figure, magnified forty times, repre

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FIG. 2. Variety Braunii genuina. sents the anterior aspect of a node of a leaf, with two sporangia, one antheridium, in situ (outlined) and one removed; only the anterior bracts are shown, the lateral are about the same length.

III. Forma meiocarpa, microptila, verticillata, elongata, clausa,