LATEX-TUBES. 247 
the (non-officinal) root-stock of Aspidium spinulosum Swartz; 
in the other ferns of our region they are wanting. 
A second form of secreting cells are the latex-tubes or latici- 
ferous ducts.’ In most cases (especially when the tubes are 
very long) they are produced, like the vessels, by the resorption 
of the transverse walls of lines of cells lying over each other 
(cell-fusion). In their simplest initial formation they are dis- 
tinguished, however, from the neighboring parenchyma cells, 
like the mucilage-cells and the oil-cells, only by their contents 
and somewhat more considerable width, as for instance in jalap 
or 
Fie. 164, : Fie. 165, 
Fig. 164.—Longitudinal section through the outer latex-zone of Radix Taraxaci, more 
highly magnified; cr, sieve-tubes; /, latex-tubes. : 
Fig, 165.—Longitudinal section through one of] the inner 
azxaci, in which the tubes (7) are accom panied by sieve-tubes (er). 
latex-zones of Rad. Tar- 
1 With regard to latex-cells and latex-tubes, compare Meyen, ae Die 
Secretionsorgane der Pflanzen,” Berlin, 1837.—Hanstein, “* Die Bilon 
saftgefiisse,” Berlin, 1864.—Dippel, ‘* Entstehung der Milcheaftgefasse, ” 
Rotterdam, 1865.—Vogl, ‘‘ Beitrage zur Kenntniss der Milchsaftorgane, 
in Pringsheim’s Jahrb., v., 31.—David, “ Ueber die Milchzellen der 
Euphorbien,” Breslau, 1872.—E. Schmidt, Botan. Zeit., 1882. Scott, In- 
augural Dissertation,” Wiirzburg, 1831, etc. 
eee 
