of Laticiferous Tubes . 161 
The following plants were investigated : — 
Euphorbiaceae : — Euphorbia Helioscopia , E. Peplus , E. Cy - 
parissias , if. puniceus , Sapium sp. 5 Manihot utilissima , var. 
dulcis. 
Papayaceae : — Carica Papaya , Jacaratia sp. 
Artocarpeae : — Pharmacosycea sp., Ficus elastica , Urostigma 
sp. 
Asclepiadaceae : — Asclepias curassavica. 
Compositae : — Hypochaeris radicata . 
Euphorbiaceae. 
Euphorbia Helioscopia (Fig. i) is admirably suited for ob- 
servation because of the extreme thinness of the leaves. The 
whole leaf was rendered transparent by chloral-hydrate. 
Tracing a wide tube from the base of the leaf, it runs and 
branches in the spongy parenchyma. All the tubes thus formed 
continue their course, here and there crossing or running for 
a short distance with a vascular bundle, and finally pass 
through the palisade-layer, terminating in a copiously branched 
subepidermal system. Occasionally a tube again dips down 
into the mesophyll. In the few cases in which I observed 
this descent into the mesophyll, the tubes branched there, 
and the branches ascended once more to the epidermis. 
Occasionally the tubes in the mesophyll give off short blunt 
processes, which showed no intimate relation with the ad- 
joining cells, but rather suggested the appearance of young 
branches. Some tubes, on reaching the edge of the leaf, bend 
inwards and may end in the mesophyll. Thus the tubes end 
in any part inside the leaf, but chiefly beneath the epidermis. 
The complicated and tortuous course of the tubes is difficult 
to reconcile with Haberlandt’s theory of conduction by the 
shortest route. 
The leaf of E. Peplus (Figs. 3, 3) is very similar to the one 
previously described. There is a well-developed system of 
subepidermal tubes beneath the lower epidermis, though that 
