850 
MR. W. GARDINER ON THE CONTINUITY OF THE 
processes when pulled out of the pit cavity in consequence of the action of strong 
sulphuric acid, or other dehydrating agents. 
The staining results with Bomarea appear to me to give great support to the idea 
that a pronounced coloration of the pit membrane by picric-HoFMANN’s-blue after 
the action of iodine and Chlor. Zinc Iod. gives evidence of the presence of protoplasmic 
threads in the cell wall and therefore of perforation. 
In Ruscus, although the cells are large, the pit membranes are very thin and 
quickly coloured with iodine and Chlor. Zinc Iod. After staining in the usual manner 
fairly well defined threads can be seen (Plate 70, fig. 29). The same is the case with 
Iris and Xiphium. 
Colchicum is a particularly plain example of perforation of the pit membranes, 
which are here somewhat thick. Both with iodine and with Hofmann’s blue the 
individual threads are easily distinguished (Plate 70, fig. 80). Of Dicotyledons exhibit¬ 
ing a similar structure, Ardisia polycephala is an example of some interest on account of 
its peculiar reaction with iodine. With a dilute solution of this reagent the substance 
of the cell-walls give a blue reaction, exactly resembling that of starch. Stronger 
solutions rapidly cause a dark brown coloration. The seeds of Ardisia crenulata 
behave in the same way. The same has been observed in the seed of Pceonia., and 
has been long known in the case of the phloem of Lycopodium; the so-called fungus 
cellulose ; and (when the iodine solution is of a certain strength) in mucilage cells. In 
Nemophila, although the cells are small, an appearance of striation is plainly evident 
(Plate 70, fig. 32). The structure of the horny seeds of certain of the Rubiacece, e.g., 
Coffea, Galium, and Aspenda (Plate 70, fig. 31) is of some interest. The cell-walls 
present a somewhat crumpled appearance, and there is no definite arrangement in 
their shape. After treatment with strong iodine and a lengthy action of Chlor. Zinc 
Iod., a system of fine threads is clearly brought into view. Where the wall is pitted, 
the threads go through the pits, or, if not, through the thick wall, as the case may be. 
This was observed in Asperula only. The rest were not examined in detail. 
The structure of the seeds of Tamus and Dioscorea axe very important as affording 
additional confirmation of Tangl’s results with Strychnos. The thick walls of these 
seeds present no pits, and are of the same transparent horny nature as those of 
Strychnos Ignatia. After treatment with iodine and Chlor. Zinc Iod. the very numerous 
threads which freely perforate the entire thickness of the cell-wall gradually come into 
view, and resemble in both arrangement and properties those of Strychnos. The fact 
that the threads cross the middle lamella is even better demonstrated in Tamus than 
in the former instance, for here the development of the lamella is not so great. The 
cell-walls soon swell very strongly, and in so doing the threads are broken up into a 
number of points, as Tangl has observed, and in the swollen portion of the wall at 
last become invisible (Plate 70, fig. 33). In Dioscorea the threads are much finer than 
in either Strychnos or Tamus. In both instances threads can be observed uniting all 
