59 
in the pith of Manihot Glaziovii. 
walls and abundant starch-contents 1 . It is worthy of note 
that in these young nodes the laticiferous tubes are not, as in 
the internodes, confined to the peripheral portion of the pith 
(see above). Their distribution thus shows a relation to that 
of the starch-containing pith, though, as we have seen, they 
may also traverse other parts of the tissue. 
In older nodes this kind of pith, though forming a thicker 
layer than in the internodes, does not extend to the centre, 
which is occupied by large slightly lignified cells, like those 
forming the internal mass of the pith in the internodes. 
It seems probable that some of the inner laticiferous tubes 
become obliterated by the pressure of these cells in their 
later growth. 
II. 
The discovery of nuclei in laticiferous tissue is due to 
Treub 2 , who in 1879 found that the non-articulated laticiferous 
tubes of the plants he investigated (Urticaceae, Asclepiadaceae, 
Apocyneae, and Euphorbiaceae) were multinucleate. The 
first to observe nuclei in articulated tubes was Dr. Scott 3 , 
who, in describing the laticiferous vessels of Chelidonium , 
mentions that they contain one nucleus to each member of 
the vessel, and that these nuclei are present as long as the 
vessel exists. 
In the next year (1882) Schmidt 4 described protoplasm and 
nuclei in the laticiferous vessels of several species belonging 
to Cichoraceae, Campanulaceae, Lobeliaceae, Papayaceae, 
Papaveraceae, Aroideae and Musaceae. His investigations 
leave little doubt that throughout these orders the laticiferous 
vessels retain the essential characters of living elements during 
their whole existence. 
1 By splitting a piece of the stem down the middle and treating it with iodine 
solution, the position of the starch-containing pith is very well brought out. 
2 Sur des cellules vegetales a plusieurs noyaux in Arch. Neerland. xv. 1880. 
3 Zur Entwickelungsgeschichte der gegliederten Milchrohren der Pflanzen. Diss. 
Wurzburg, 1881. Also in Quart. Journ. Microscop. Science, 1882, p. 152. 
i Bot. Ztg. T882, Nos. 27 and 28. 
