THE ANNALS 



AND 



MAGAZINE OF iN AT URAL HLSTOHY. 



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 Avorthy 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 ilattened frond, rather 

 suddenly constricted into a delicate cylindrical stipes. With 

 respect to these dififerent 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. ^ Ma(/. N. Hist. Vol. ix. G 



