4 SMITH: THE HISTOLOGY OF CERTAIN ORCHIDS 
Walliczek studied the slimes of the inner vegetative tissue 
of Tilia grandiflora, Tilia parviflora, Hibiscus syriacus, Theo- 
broma Cacao, Althaea taurinensis, Rhamnus Frangula, and the 
following, cacti: Epiphyllum, Echinopsis Eyriesiit, E. multiplex, 
Mammiilaria densa, and Opuntia Tuna. In no case does he con- 
sider these as cell content slimes, although in discussing the 
slime of cacti he says that the mucilage is laid down upon the 
primary wall as a secondary thickening, but that the primary 
wall has no active part in the process, and that the cytoplasm, 
as the laboratory of the cell, is in each case (species of Epi- 
phyllum) the builder of the deposits of slime, which are, however, 
never found within the primordial utricle but always outside it. 
He describes the stages in the development of the mucilage 
cells in Tilia grandiflora, these including the enlargement of the 
cells and the increase in density and amount of the cytoplasm 
and nucleus. By the deposit of mucilage these are pushed to the 
center of thecelland finally in the mature cell have the appearance 
of undergoing disintegration. He says the slime is laid down 
centripetally, that when it dissolves the inner part disappears 
first, and that during their develo t neither the slime cells nor 
those surrounding them contain chloroplasts or starch. The 
process of mucilage formation is a very quick one. Later the 
mucilage begins to dissolve and the dissolved slime seems to be 
changed into starch. At least the slime cells of the cortex in 
Tilia grandiflora, which show stages of mucilaginous disinte- 
gration, are densely filled with starch, as are also the neighboring 
cells and no others. He has studied the history of the slime cells 
in this species with reference to their changes with age and 
concludes that noticeable changes may not occur until the third 
year, when the slime cells may show only traces of stratification 
on the primary cell wall. In other cells the disappearance of 
slime was much longer delayed and he found eight year old 
slime cells which were little changed in appearance from newly 
formed ones, though his general conclusion is that in all cases 
the slime of the inner tissue is at least in part dissolved and 
taken up in the metabolism. 
In the case of Scilla maritima, Symphytum officinale 
and Orchis tubers he thinks without doubt that the slime is 
a store of reserve food (Tschirch). The function of slimes in 
general he thinks is that of storing water which can be distrib- 
uted to the surrounding tissue in time of need. 
