Watson on Structure and Relation of the Plastid. 343 



no regular direction or sequence. Tlie interplastid fibres are 

 shown joining them. 



The group of three plastids marked Pj 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 P4) 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. 



Cypripcdium 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. 



Dicffcnbachia. — 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 



