An Account of the Veins and Arteries of Leaves. By Frank Nicholls, M. D. Prael. Anat. Oxon. F. R. S.

fio fuit $9^h 27' 53''$ in recta cum Galilaeo, & Lansbergio. Emersio vero $10^h 24' 17''$ in recta cum Macrobio & Sosigene. *Mart.* die 2 Vesp. occultavit Luna Stellam $\gamma$ *Cancri*. Immersio fuit $8^h 14'$ in recta per Copernicum & Boreum marginem Langreni. Emersio fuit neglecta. *Maii* die 24 Summo Mane $1^h 51' 30''$ Luna absorbit Stellam $\tau$ *Scorpionis* proxime Byrgium. Emersio non fuit observata. *Sept.* die 14 Vesp. Luna occultavit Stellam $\eta$ *Capricorni*. Immersio fuit $8^h 11' 20''$ inter Seleucum & Cardanum. Emersio $9^h 37' 30''$ paulo infra Langrenum. Die 19 Vesp. Luna obtexit Stellam $\delta$ *Piscium*. Immersio fuit $8^h 43' 45''$ in recta per Tychonem & Langrenum. Emersio autem $9^h 5' 15''$ in recta cum Tychone & Keplero. *Oct.* die 28 Manè Luna occultavit Regulum, seu Cor Leonis Immersio fuit $1^h 39' 50''$ in recta per Aristarchum & Gassendum. Emersio $2^h 11' 15''$ in recta per Aristarchum & Cardanum. --- V. An Account of the Veins and Arteries of Leaves. By Frank Nicholls, M.D. Prael. Anat. Oxon. F.R.S. By a Letter from Dr. Fuller in Holland to the President, and communicated about October last, the Society was informed, that the ingenious Professor Ruyssch had observed something in the dissecting of Leaves analogous to the Veins and Arteries of Animals; but without explaining in what Manner these different Vessels were disposed, or by what Means they may be distinguished from each other. When I had the Pleasure of examining the Collections of Frederick Ruysch and Albert Seba at Amsterdam, in both which were great Variety of dissected Leaves, they made no Mention of such Discovery; although in a Leaf from the Collection of Ruysch, I could (with a Glass) observe the Fibres to be double towards the Edges of the Leaf; which at that Time I imagined to be an unnatural Division of the Fibres, as in decayed Sticks. In the mean Time, Albert Seba having communicated the Method of dissecting Leaves to the Society, by a Letter to the President, I separated the pulpos from the fibrous Parts of several Leaves after his Method; when examining them by Glasses, and in Water, I found that each Fibre was naturally separated into two distinct Fibres by a thin Stratum of the pulpos Substance; and that this Separation was continued through all the Fibres and Stem of the Leaf, so as to form two distinct Planes of similar Net-work. Though this Duplication of the Vessels in Leaves seems to point out an Analogy between them and the Veins and Arteries of Animals, yet I see no probable Means of guessing which are the arterial and which the venal Fibres. That I might illustrate this Matter, as it appeared to me, I have prepared two Leaves, the one of an Apple, the other of a Cherry; in which, as well the Separation of the Fibres and Stem, as the pulpos Substance, by which they are naturally separated, are very obvious. See Plate II. A the Cherry-Leaf; B the Apple-Leaf, whose Planes are separated. Both which (the Society having nothing of this Nature in their Repository) I desire may be accepted as a Mark of the Respect of their Most Humble Associate, June 11, 1730. F. Nicholls.