THE LATICIFEROUS CELLS OF THE EUPHORBIACER. 447 
distinct and excentric hilum exist, one notices that the hilum 
is always on that side of the starch-grain which is furthest from 
the place of deposition. 
* If one observes cells with starch-grains which are even in 
their earliest stages of development, one sees that, at the end 
which is in contact with the protoplasm or chlorophyll-corpuscle, 
generally a layer of a substance is deposited which is distinguished 
optically from the protoplasm or chlorophyll-corpuscle and from 
the starch-grain. On treatment with iodine one sees that this 
outermost layer of the starch-grain is not coloured blue, and that 
it is not stained so deep or dark a brown as the protoplasm or 
chlorophyll-corpuscle. 
* I consider that this layer, which is always present, though 
difficult sometimes to see unless earnestly sought for, to be a 
substance which will become starch, but which has not the pro- 
perty to stain blue with iodine, and which moreover (perhaps) 
contains nitrogen or protein substance.” 
This layer Crüger calls intermediate substance (“ Uebergangs- 
substanz "). With special reference to the Euphorbiacee he 
remarks :— 
“The development of the cut-off or knotty rods, which arise in 
the so-called remarkableevessels of the Euphorbiacee, agree with 
those described above in so far that the young grains are round. 
Layering, or intermediate substance, or a polarization-cross I 
could not observe.” 
Portions of laticiferous cells in Euphorbia splendens. a. Nuclei. The other 
elongate dark-centred cells (unlettered) represent starch-grains enclosed in the 
starch-forming corpuscle. 
