THE ANNALS AND MAGAZINE OF NATURAL HISTORY. No. 56. APRIL 1842. IX. — Contributions to Structural Botany. By W. Hughes WiLLSHiRE, M.D., M.B.S., Lecturer on Botany at Charing Cross Hospital. 1. — Specimens of Ulva calophylla, Spreng.^ having lately been transmitted to the Botanical Society of London, I have had an opportunity of fully examining this curious alga, and it appears to me worthy of some remark, both as regards its structure and its relative affinities. Under the microscope several forms of the plant may be seen, and which to me ap-pear to be permanent, at least whatever form perfects its qua-ternary granules I think should be looked upon as a perfect plant : this may either exist as a cylindrical cellular filament continuing of the same diameter throughout its whole length, except close to its fixed extremity, where it becomes slightly attenuated and rounded, and is more or less conical at the op-posed one ; it undergoes no alteration or change of form, but two rows of quaternate granules are produced in the cellular cylinder ; — it may be observed as a flattened strap or band of a breadth equal to four or five diameters of the filament or even more, becoming considerably attenuated towards its fixed extremity, and is more or less constricted at distant intervals, a membranous band being seen at the points of constriction ; — lastly, it may be seen as a very broad flattened frond, rather suddenly constricted into a delicate cylindrical stipes. With respect to these different conditions, I would observe, that the first or cylindrical one is not necessarily to be regarded as an imperfect condition of the others, or as one that must neces-sarily, at an after period of the life of the plant, pass or become metamorphosed into them. Except in the earliest stages of the life of the plant, in whatever condition of age or form it may be observed, it will be found that the margins of the band or strap, and the circumference of the cylinder, are brightly transparent; that the flattened frond is traversed longitudi-nally by transparent lines, varying in number according to the breadth of the strap, and between which are placed green-Ann. ^ Mag. N. Hist. Vol. ix. G
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