CHAP. I. 
CELLULAR TISSUE. 
19 
5. Fibres forming distinct arches, as seen in the anthers of 
Lin aria cymbalaria, &c. by Purkinje. (Plate T. fig. 4.) * 
In the centre of some of the bladders of the cellular tissue of 
many plants there is a roundish nucleus, apparently consisting 
of granular matter, the nature of which is unknown. It was 
originally remarked by Francis Bauer, in the vesicles of 
the stigma of Phaius Tankervilliae. A few other vegetable 
anatomists subsequently noticed its existence; and Brown, 
in his Memoir on the mode of impregnation in Orchidacese 
and Asclepiadacese, has made it the subject of more extended 
observation. According to this botanist, such nuclei not only 
occasionally appear on the cuticle of some plants (Plate III. 
fig. 9.), in the pubescence of Cypripedium and others, and in 
the internal tissue of the leaves, but also in the cells of the 
ovule before impregnation. It would seem that Brown con- 
siders stomates to be formed by the juxtaposition of two of 
these nuclei. {See also Slacks in the. Trans. Soc. Arts, xlix.) 
Dr. Schleiden has published some extremely interesting 
observations upon this body, which he regards as a universal 
elementary organ, and calls Cytohlast.\ According to this 
observer, the form varies from oval to lenticular and round, 
the colour from yellowish to a silvery white, and changing to 
pale yellow up to darkest brown upon the application of 
iodine: in size it varies between 22 V 0 ^ Paris inch in 
diameter, in Fritillaria pyrenaica, where it attains its largest 
size, and embryonal end of the pollen tube of 
Linum pallescens. In structure it is usually granular; in 
consistence it varies between extreme softness and such a 
degree of toughness, as enables it to resist the pressure of the 
compressorium without altering its form. In the interior of 
the Cytoblast, or sunk in its surface, is a small, well-defined 
* According to the last mentioned author, the fibres themselves are 
generally tubular, and either perfectly round or somewhat compressed, or 
even three or four sided. He considers it proved that they are hollow, by 
their appearance when compressed, by their occasionally containing bub- 
bles of air, and by the difference between their state when dried and when 
recent. 
f 1 regret very much that my imperfect acquaintance with the German 
language is insufficient to enable me to give the valuable observations of 
this excellent observer more in detail. 
c 2 
