17© Col. Velley's Defcripilon of Conferva umbilicata. 



membranaceous, leaves, giving the frond the form of an umbilicarecf 

 Ulva. Under the microfcope feveral cylindrical ftems, not larger 

 than a hair, were found to diverge fuddenly in different direftions, 

 producing fimilar ramifications in diftin<St whorls at fmall diftances, 

 and' carrying with them innumerable reticulated ramules combined- 

 together in all direftions ; fome of which feemed in a fmall degree 

 to favour a circular tendency : the whole forming a mofl beauti- 

 ful web of cylindrical filaments, far exceeding the fineft lace, and 

 fetting at defiance the utmort art of the pencil. The interftices do 

 not retain any regular or prevailing form throughout, as they ap- 

 pear to do in the Conferva reticulata ; but are united with each 

 other in the manner above mentioned. 



Two circumftances are to be obferved in the ftrufture of this 

 plant. Firft, the ramules, however varied in their direftion, unite 

 with the main ftems at regular joints ; while the feparations, or 

 diaphragms, as they are generally called in the Conferva, are evi- 

 dently apparent at thofe points of union. Secondly, between the 

 interftices fmall fubacute fpinules frequently appear. Hence I 

 was induced to confider this vegetable produftion, however Angu- 

 lar in its mode of growth, as a real Cotferva. As the ramifications 

 brought to my mind the veins of a leaf, I at firft examined it under 

 a notion of its being the fkeleton of fuch a body, after it had been 

 diverted of its cellular fubftance : but as this web fo greatly fur- 

 pafTes in tenuity any of thofe appearances, I conclude it could never- 

 have continued in fo diftintft and organized a flate, if its prefent 

 form had been owing to an anatomical procefs, which fometimes ac- 

 cidentally takes place in decayed leaves. 



..The filaments, feparately viewed, were traufparent, but contracSled 

 a degree of opacity at the joints. The whole plant, from the clofe- 

 nefs of its texture, when taken in the mafs, has a fombre green 

 tint. 



XIX. Ob. 



