86 
Walter Gaudiner. 
Final conclusions. 
I will now briefly sum up my principal results. At the oulsel I may 
point out that they have all been obtained with fresh material, which appears 
to me to considerably increase their value; although as 1 have shown alcohol 
material may be employed. I am aware that most of the observations have 
been made upon thick-walled tissue, in consequence of the fact that the 
thinner the pit-membrane the rnore difficult does observation become. 
But in allied genera and species, some of which show the exislence of 
a continuity, and some do not, there seems to be but little doubt that the 
same strueture is in reality common to them all. 
As regards the modes in which the continuity of the protoplasm of 
adjacent cells is maintained, I have eslablished in the material upon which 
1 have worked. 
1. That in pitted cells the pit-membrane is traversed by numerous deli— 
cate protoplasmic filaments, connecting the protoplasmic processes 
which occupy the pit-cavity, on each side of the common closing 
membrane; 
2. That in unpitled cells e. g. Tamus, Strychnos, Dioscorea, very delicate 
protoplasmic filaments traverse the cell-wall throughout ils whole 
extent. Such cells are however of rare occurrence; 
3. That in some cases, e. g. Lodoicea, Bentinckia, Howea, and Kentia in 
which the cells are pitted, these delicate protoplasmic filaments 
traverse not only the pit-membrane, but also the general cell-wall; 
i- That the significance of pits is to alf'ord a means of communication 
between adjacent cells through the agency of the porous pit-mem¬ 
brane. 
Front the observations mentioned under section 3 1 am inelined to 
believe that the passage of protoplasmic filaments through the unpitted 
portions of cell-walls is by no means uncommon, but the demonstration of 
this is difficult owing to the extreme fineness of the filaments. As regards 
the significance of the various structures described, I am of opinion that in 
all cells whatsoever the walls are perforated, and that the perforatious are 
traversed by protoplasmic filaments. Thus sieve-tubes must be regarded 
as merely special examples of a general strueture. 
Taking all the cases, in which the passage of protoplasmic filaments 
from cell to cell has been demonstraled we find that they present great 
Variation as regards the size of the channels. The largest and coarsest form 
is aflbrded by such structures as sieve-tubes; next come the perforalions 
in endosperm cells in which the whole strueture is more delicate, and linalls 
the perforations in pulvini and the like, which are excessively fine. But 
the general principle or type of strueture is the same throughout, though in 
some cases the perforations are confined to limited areas of the cell-wall 
