JOURNAL OP MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATE XIX, 

 Illustrating Mr. Francis Darwin's Paper on the Protrusion 

 of Protoplasmic Filaments from the Glandular Hairs on 

 the Leaves of the Common Teasel {Dqjsacus sylvestris). 



Fig. 1, — A trichotne of the kind which neither secretes resin nor pro- 

 duces filaments, x 420, camera lucida, Hartnack obj. No. 8. 



Fig. 2. — Gland bearing a long and stout filament. X 420, camera, 

 Hartnack No. 8. 



Fig. 3. — Gland bearing a simple filament and two other small proto- 

 plasmic masses, one cylindrical, the other partly spherical. X 420, 

 camera, Hartnack No 8. 



Fig. 4. — The same gland, showing the three masses united into one 

 through contraction produced by dilute acetic acid. 



Fig. 5. — Summit of a gland bearing a filament killed by one per cent, 

 osmic acid, and afterwards changed into a "soap-bubble" mass. X 420, 

 Hartnack No. 8. 



Fig. 6. — Gland bearing a complicated mass of filaments, consisting 

 either of a single branching filament, or of several entangled together. 

 X 170 {camera sketch), Hartnack No. 5. In this drawing the jilament 

 is represented by a single line. 



N.B. — The filament was in movement, and continually changing its 

 appearance, so that it was impossible to copy it with absolute fidelity. 



Fig. 7. — Gland from specimen which had been mounted about a quarter 

 of an hour previously, in ^ per cent, carbonate of ammonia. It 

 shows the characteristic rounded masses of delicate transparent proto- 

 plasm which exhibit amoeboid movements. X 420, sketched with camera^ 

 Hartnack No. 8. 



Fig. 8. — Gland with filament in the condition in which slow changes 

 of form occur from some unknown cause (see p. 262). X 420, sketched 

 with camera, Hartnack No. 8. 



Fig. 9. — Same gland, showing the changes which have taken place 

 within half an hour. Fig. 9 also illustrates the "mouiliform" condition 

 which often precedes contraction. 



Fig. 10. — -Aggregation of the cojitents of a gland into amoeboid masses. 

 From a specimen left in water from August 22 — 26, and which was 

 therefore exposed to a nitrogenous fluid. X 500, camera, Hartnack No. 9. 



Fig 11. — From a specimen left in infusion of meat from July 20—26. 

 Besides the three glands are shown enormous masses of highly refracting 

 protoplasm, which underwent spontaneous changes of form. (Dotted 

 lines show a doubtful union of two portions.) x 255, camera, Hartnack 

 No. 5. 



Fig. 12. — Part of a large, simple, non-glandular hair from a seedling 

 leaf; the protoplasmic network has thrown out three filaments (marked *), 

 which project freely into the cell-sap. X 420, sketched with camera, 

 Hartnack No. 8. 



Fig. 13. — Well-developed gland, containing drops of resin within 

 gland-cells. X 420, camera, Hartnack No. 8. 



Fig. 14. — Freely floating mass of protoplasm, x 500, camera, Hart- 

 nack No. 9. 



Fig. 15, A, B, and C. — A free mass of protoplasm in active movement. 

 Sketched with camera three times in five minutes, x 630, Hartnack 

 No. 8. 



Ftg. 16. — Transparent filaments (looped and branching), from speci- 

 mens treated with ^ per cent, carbonate of soda, x 420, camera, 

 Hartnack No. 8. 



