Dovlk — Observations on the Morphology of Larix Icptolepis. 329 



EXPLANATION OF PLATES. 



Plate XVII. 



All of Larix leptohpis. 

 Figs. 



1. L. S. of male bud, showing secretory sacs in microsporophyll 



knob, (x 35.) 



2. T. S. of same. A = secretory sacs of microsporophylls below. 



(x 30.) 



3. T. S. of vegetative bud, showing secretory canals for comparison 



with fig. 2a. (x 25.) 



4. Portion of epidermal wall of microsporangium, showing stomium. 



(x 50.) 

 5, 6, 8. Mature pollen grain, (x 350 approx.) 



7. Photomicrograph of grain drawn in fig. 6. (x 350 approx.) 

 9-13. Various double grains, (x 350 approx.) 



14. A grain already irregularly divided, though not yet separated from 



its tetrad fellows, (x 350 approx.) 



15. Grain just rounded after tetrads, (x 350 approx.) 



16. Spireme of first division, to show passive nucleoli, (x 350 approx.) 

 17, 18. Cutting of first normal prothallial. (x 350 approx.) 



19. Prothallial nucleus returning to resting stage if sufficient cyto- 

 plasm, (x 350 approx.) 

 20, 21. Oblique spindle of first division, cutting off one-third of the 



primary cell, (x 350 approx.) 

 22, 23. Spindle at right angles to normal plans, dividing primary cell into 

 two equal ones, (x 350 approx.) 

 24. No wall formation at first division, leaving two free nuclei in the 

 cytoplasm, (x 350 approx.) 



Plate XVIII. 



1. Normal second prothallial cell formed, (x 350 approx.) 



2. Second prothallial following a first division, which had cut off 



one-third the primary cell, (x 350 approx.) 



3. A double pollen grain, with the vestiges of the wall round the 



generative nucleus appearing in one half, (x 350 approx.) 



4. Normal division in formation of stalk and body cells, (x 350 



approx.) 



