465 
Peirce. — Studies of Irritability in Plants. 
Fig. 5. Fimbriaria Californica. Germinating spore, fourteen days after sowing, x 84. 
Note directions of growth and of cross-walls. 
Fig. 6. Gymnogmmme triangularis. Spores germinating under constant electric light, almost 
five weeks after sowing, light only from direction of arrow, x 300. 
Note directions of growth of germ-tubes and of cross-walls. 
Fig. 7. Gymnogramme triangularis. Spores germinating on Knop’s solution sixteen days after 
sowing, light from direction of arrow, x 300. 
Note directions of germ-tubes, rhizoids, and cross-walls. 
Fig. 8. Gymnogramme triangularis. Diagram showing directions of rhizoids of young plants 
sixteen days after sowing on Knop’s solution revolved on clinostat. x 70. 
Fig. 9. A. fusiformis. Young plant almost seven weeks after sowing on \ hour clinostat 
revolving culture of unsterilized soil, x 41. 
Fig. 10. A. fusifomiis. Young plant of same date ot sowing, culture receiving light from 
direction of arrow, x 41. 
Fig. 10 a. A . fusiformis. Optical section of plant shown in Fig. 10. x 41. 
Compare radial form of Fig. 9 and dorsiventrality of Figs, 10 and 10 a. 
Fig. 11. A. Pearsoni. Young plants just over six weeks after sowing on one hour clinostat 
revolving culture of sterilized soil, x 41. 
Fig. 11#. A. Pearsoni . Young plant of same date of sowing, culture receiving light from 
direction of arrow, x 41. 
Compare this with Fig. 11 as to form. 
Fig. 12. Fimbriaria. Young plants almost five weeks after sowing on \ hour clinostat. x 41. 
Fig. 12 a. Fimbriaria . Young plant of same date of sowing, culture lighted from direction of 
arrow, x 41. 
Fig. 13. Fimbriaria. Young plant 5! weeks after sowing on one hour clinostat, going over to 
dorsiventral form. x 41. 
Fig. 14. Gymnogramme. Prothalli almost five weeks after sowing on £ hour clinostat. x 41. 
Fig. 14#. Gymnogramme. Prothalli of same date of sowing, culture receiving light from 
direction of arrow, x 41. 
Fig. 15. Gymnogramme. Prothallus seven weeks after sowing on one hour clinostat. x 41. 
Rhizoids and reproductive organs on both sides. 
Fig. 16. A. fusiformis. Young plant almost nine weeks after sowing on one hour clinostat. 
x 41. 
Note half-round form on slow clock. 
Fig. 17. Dictyopteris polypodioides. Young plant in dish of sea- water on shelf, receiving light 
from one side only, x 125. 
Fig. 17#. Dictyopteris polypodioides. Young plant twenty-three days after sowing in sea-water 
on one hour clinostat. x 125. 
