Some Studies on the Structure of the Plant Cell by 
the Method of Dark-ground Illumination. 
BY 
S. REGINALD PRICE, M.A. 
With Plates XLI and XLII. 
Table of Contents. 
PAGE 
§ i. Historical and Introductory . 601 
§ 2. The Present Work 603 
§ 3. Observations of Living Cell 
Structures 605 
§ 4. Some Fungus Spores and their 
Germination 61 1 
§5. The Sap Particles or Inclusions 613 
§ 6. The Nucleus 615 
§7. The Chloroplast 617 
PAGE 
§ 8. Some Studies of Plasmolysis : 
( a ) Appearance in Various 
Cases 618 
( b ) The Protoplasmic Fibrils . 621 
§9. The Action of Fixing andother 
Reagents on the Plant Cell 623 
§ 10. Discussion and Conclusions. . 626 
Summary 629 
§ 1. Historical and Introductory. 
I T may be fairly said that until ten years ago — that is, till the year in 
which Siedentopf (’03, pp. 1 - 39 ) elaborated the method of the ultra- 
microscope — the method of dark-ground illumination with the microscope 
was regarded as a means of exhibiting objects with striking and pretty 
effect, rather than a means of observation of minute structure and of 
scientific research. Siedentopf and Zsigmondy (’03), by using a powerful 
beam of light projected perpendicularly to the axis of the microscope, 
showed that particles could be exhibited which were beyond the range of 
possible resolution with the ordinary transmitted light. No direct light 
enters the microscope ; the small particles scatter the light, and by reason 
of the diffraction images so produced, they appear as though they were self- 
luminous against a black background. There is no need in this place to 
deal with the development of the method of dark-ground illumination for 
high power work since that date, but reference may be made to several 
published accounts of the subject (Thirkill, ’09 ; Spitta, ’09, pp. 173 sqq. ; 
Price, T3, and so on). 
The study of colloidal hydrosols by this method was first carried out 
by Zsigmondy (’09), and since then the method has become a great factor 
Annals of Botany, Vol. XXVIII. No. CXII. October, 1914.] 
