1 86 Beer . — Development of the Spores of Helminthos tacky s zeylauica . 
EXPLANATION OF PLATES XI AND XII 
Illustrating Mr. Beer’s paper on the Spores of Helminthosiachys. 
PLATE XI. DRAWINGS. 
Fig. i. Tapetal cells, x 660. 
Fig. 2. Nest of nuclei lying at the inner periphery of the disintegrating tapetum. a , a 
constricted nucleus which is probably dividing amitotically. x 850. 
Fig. 3. Chromosomes during first division of the spore-mother-cell, x 1100. 
Fig. 4. Spindle and chromosomes during first division of the spore-mother-cell, x 850. 
Fig. 5. Daughter-nuclei resulting from first division of the spore-mother-cell, x 1100. 
Fig. 6. Tetrad showing the very young spore-wall (left white) surrounded by the special- 
mother-cell wall (drawn black), x 850. 
Fig. 7. Tapetal plasmodium. Nuclei passing into one of the cytoplasmic strands which reach 
into the interior of the sporangium, x 850. 
Fig. 8, a and b. Young spores. In b the wall has separated into three flaps at the ridges. 
X 850. 
Fig. 9. Apex of young spore; showing little fold of endospore in section, x 850. 
Figs. 10 and n. Nearly mature spores. Fig. 10 looked at from above; Fig. 11 in section. 
Both x 850. 
Fig. 12. Tapetal nuclei from a sporangium in which spores had thickened, but still smooth 
exospores, x 850. 
Fig. 13. Nuclei from tapetum of mature sporangium. 
Fig. 14. Nucleus from tapetal plasmodium of a sporangium in which the young spores were 
surrounded by a thin exospore. Amitosis (?) x 850. 
PLATE XII. PHOTOGRAPHS. 
Fig. 15. Young sporangium; tapetal cells surrounding the spore-mother-cells. The break 
in the mass of mother-cells is caused in preparing the section and does not indicate a natural 
separation of these. 
Fig. 16. Spore-mother-cells surrounded by the tapetal plasmodium. The tapetal membranes 
have all disintegrated. 
Fig. 1 7. Early stage in the separation of the spore-mother-cells from one another. T" ' first 
lines of the mucilaginous degeneration of the middle lamellae are shown. 
Fig. 18. The young tetrads (special-mother-cells) with tapetal plasmodium gradually flowing 
between them. 
Fig. 19. Older stage, showing distribution of tapetal plasmodium between the spore-tetrads. 
The young spores have all collapsed in the alcohol. 
Fig. 20. Almost mature spores. The plasmatic membranes of the tapetal plasma still 
surround the spores. The spores to the extreme right of the figure show the little fold of endospore 
penetrating the cleft in the apex of the exospore. 
