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821 
Original Articles. 
ON * TYLOSES," THE CELLULAR FILLING UP OF VESSELS, E 
By W. T. TursErvToN Dyer, B.A., B.Sc., F.L.S. 
(PLATE ped 
are th Report apers on Bota The volume for 2 contains 
Mohl’s important memoir upon th Palm Ste n e following 
passage occurs n the porous vessels of the Dico'ylodons it is well 
composed of the same membrane which forms the wall o "the e porous 
vessel, whence he assumed (Fhyiot omie, Pe 237) that such vesicles could 
y no means occur in the Monocotyledons. I, however, found, though 
indeed but seldom, ge Se ae similar to those of the Dicotyledons, 
in the large vessels of the , for instance, in Corypha cerifera." 
And he adds in a note :—* I n Ke traced the development of these 
cells in the Fates. Doubtless they have the same character as in the 
Dicotyledons, in regard to which, from recent researches, I think that I 
am not wrong in assuming E they are prodi bya protruding gens 
sion (a kind of kern ia) of the adjacent cell, which penetrates the pore 
and either tears through or causes the gina G of the primary mem- 
ne of the vessel." 
a 
was, therefore, very pleased to find an illustration of it in a preparation 
purchased from Professor Van Heurck, of Antwerp, and labelled “ Ty- 
loses dans la Vigne.’ 
Shortly afterwards, when examining some microscopic sections of fossil 
Wood of eocene age, preserved in the Botanical Department of the British 
Museum, I recognized the same gear filling up of the ducts which I 
was already familiar with in the Vin 
I applied to Professor Van Heurck for some information as to any 
accessible account of “ Tyloses." He kindly referred me to a paper pub- 
lished anonymously (in the * Botanische Zeitung’ for 1845), but which he 
attributed to the Pamens Hermine von Reichenbach. In this paper 
the cells ‘a a in vessels are termed **thyllen," and from this, I 
iei oe F i derived, though in what way I do not exactly 
These are, no doubt, the rend researches alluded to by Mohl in the 
Passage quoted above. An account of them is given by Link, in the 
* ‘Report on Physiological Seer in the same volume of the Ray 
Soci lety's Publications: (pp. 237, 238). I quote some passages from it :— 
These cells ad not generally formed while the plant is young ; 1n the 
first pnm shoots of Vitis vinifera and Sambucus migra, as also In the 
stems of Civit Pepo, the vessels were empty in summer ; towards the 
N.S. VOL. I. [NOVEMBER 1, 1872. Y 
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