JOURNAL OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATE Y, 



Illustrating Dr. J. Braxton Hicks's paper on the Develop- 

 ment of the Gonidia of Lichens in relation to the 

 Unicellular Algae, &c. 



Fig. 



1. Collema-gouidia. a, as Clilorococcus ; b, Gleocapsoid. 



2. One form of development of CoUema-gonidia into Nostoc. «, early 



clianges ; b, later ditto. Mucous coat of both dark purple. 



3. Ditto, ditto. Mucous coat now colourless. 

 <t. Commencing Nostoc. 



5. Section of Collema thallus, including early Nostoc balls. 



6. Nostoc balls after extrusion. 



7. Young Collema from Nostoc balls. 



8. Collema- and Nostoc-gonidia developing into Nostoc. 



a. Early (Gleocapsoid) bodies. 



b. First appearance of linear arrangement. 



c. Early Nostoc ball, in which the vesicular cells (heteroeysts) are 



first appearing. 



d. True Nostoc. 



e. Cells of a Gleocapsoid mass undergoing binary segmentation. 



9. Changes occurring within young Nostoc. 



a, b. Approaching the linear Nostocachese. 

 c. Some reverting to Nostoc. 



10. Changes of the moniliform threads (sporidia?) within mature Nostoc* 



ultimately reverting to Nostoc. 



11. Formation of colourless fibre of Collema within Nostoc. 



12. „ epidermic layer on surface of Nostoc. 



13. Section of Collema, the Gleocapsa change proceeding within Ihe 



thallus. 



a. Gleocapsa formed from them after extrusion. 



b. Segmentation going on to form a large mass. 

 <r. One in quarternary subdivision. 



H. Section of young Apothecium of the Gyrauocarpous Licten (fig. 14), with 

 unchanged Gonidia. 



15. Section of mature Apothecium ; the Gonidia changed into Nostoc 



masses ; b, a Theca with spores. 



16. Portion of gonidial layer of same ; the Gleocapsoid change commenc- 



ing in one. 



17. Different stages of the Gonidia of same towards Nostoc. 



18. Ditto, more advanced. 



19. Eully formed Nostoc from Gonidia, as in fig. 15. 



20. Nostoc, including a bluish-green articulated thread, arising from a vesi- 



cular cell. 



21. 22. Nostocacheae, found in close relation with Nostoc. 



