Watson on Structure and Relation of the Plastid. 343 
no regular direction or sequence. The interplastid fibres are 
shown joining them. 
The group of three plastids marked P, would seem, at 
first sight, to have come from the larger plastid (s), to which 
they are all attached. Such, however, is probably not the 
case. On closer examination, each of the three is in its 
turn joined by fibres. Thus either they came from the large 
one (s), or were budded off from their adjacent predecessors. 
In either case there is left necessary an explanation of the 
interplastid fibre. This question will be treated in the con- 
clusion, so it suffices here to mention it. 
There are also conspicuous fibres joining the plastid sys- 
tem to the nucleus. Within the plastids are clear refractive 
bodies. Fig. VIII (P3 and P,) shows two stages of division 
of this body, and, judging from these and others, I believe 
this dense refractive body is a definite element in the make-up 
of the plastid. 
Cypripedium insigne.—The plastids here are of a rather 
irregular outline and stain densely with eosin. The draw- 
ing, Fig. XI, represents them as structureless ; but they have 
a finely granular appearance, that contrasts with the repre- 
sented granular protoplasm. 
No interplastid fibres are shown, but since making the 
drawing I was enabled in an acetic acid mount to make out 
very distinct strands of a marked refractive nature joining 
the plastids together. 
The systems are quite plain, but seem much more diffuse 
and less easily isolated than in such plants as Funaria. The 
observations were made on freshly cut leaf sections mounted 
in water, also killed and mounted in acetic acid. 
Dieffenbachia.—The plant was chosen to represent a high 
type of specialization, and proved valuable material. The 
subepidermal tissue in this is very abundantly supplied with 
plastids, while in the deeper tissue, that stores masses of 
starch, the plastids are much fewer and of a smaller, less 
dense character. The interplastid fibres are very numerous 
