of Laticiferous Tubes. 159 
of substances which are usually supposed to be useless excre- 
tions 1 . Up to this point then no positive statement can be 
made concerning the functions of laticiferous tubes. It may 
be that they play different parts in different plants. 
Haberlandt 2 has recently endeavoured to confirm the view 
that laticiferous tubes conduct carbohydrates. He observed 
the distribution of the tubes in leaves. He finds that the 
laticiferous tubes branch especially copiously beneath the 
palisade-cells which form essentially the chief assimilating 
system of the plant. Moreover, the free tubes which branch 
off from the vascular bundles very often direct their course 
upwards, and push up between the palisade-cells in order to 
receive the products of assimilation direct from the assimi- 
lating cells. The tubes frequently branch beneath the pali- 
sade-cells ; whilst the latter often incline in small tufts towards 
the branches. When this mode of direct communication 
is not possible, funnel-shaped collecting cells are inserted 
between the tubes and the assimilating cells. Haberlandt 
also finds that the development of an extensive laticiferous 
system in leaves is accompanied by a corresponding diminu- 
tion in the conducting parenchyma. Pirotta and Marcatili 3 , 
are led, by numerous anatomical observations, to support 
Haberlandt ’s view. 
It may however be pointed out that this supposed mode 
1 Schullerus’s assumption that latex has a relatively large amount of proteids is 
at variance with published analyses. The microchemical methods used by Schul- 
lerus were inadequate, considering the variety of substances present. In testing 
for proteids he ignored the facts that sulphuric acid will give a reddish colour with 
other substances, with some resins, with fatty acids and sugar, etc. ; iodine would 
colour the tannin, whilst Fehling’s sugar test is unsatisfactory in the presence of 
dissolved proteids. 
2 G. Haberlandt, Ueber die anatomische Beziehung des Assimilationssy stems zu 
den Milchrohren, in Sitzungsberichte der Wiener Akad., Bd. LXXXVII, 1883; Id. 
Physiologische Pflanzenanatomie, p. 226; Id. Ueber das Assimilationssystem, in 
Berichte d. deutschen bot. Gesellschaft, Bd. IV, p. 208, 1886. 
3 Pirotta e Marcatili, Sui rapporti tra i vasi laticiferi ed il sistema assimilatore 
nelle piante, in Annuario d. R. Instit. Bot. di Roma, Anno II, fasc. 1, p. 48 ; Id. 
Ancora sui rapporti tra i vasi laticiferi ed il sistema assimilatore nelle piante, ibid. 
Anno II, fasc. 2, p. 156. Marcatili, I vasi laticiferi ed il sistema assimilatore, ibid. 
Anno III, fasc. 1, p. 17. 
