214 Beer. — Studies in Spore Development. 
Fig. 13. Generative cell of pollen-grain being cut off. Cytoplasm of this cell, consisting chiefly 
of kinoplasmic fibres, can be seen. 
Fig. 14. Generative cell and nucleus at a later stage. 
Fig. 15. Tube nucleus of pollen-grain during the reconstruction of pollen-protoplast. 
Fig. 16. Similar nucleus to that represented in Fig. 15. Note chromatic sheath round nucleolus 
has separated from nucleolar substance at one point. 
Fig. 17. Wall of a nearly mature pollen-grain. 
Fig. 18. The same in surface section. 
Fig. 19. Spine from exine with dichotomously branched apex. 
Fig. 20. Tapetal cell with deeply staining fibres and granules lying in its cytoplasm. 
