PLATE HI. 



Fig. 1. Petrosia trimcata ; natural size, . 



Fig. 2. Petrosia hispida ; natural size, . 



Fig. 3. Petrosia similis, repent form ; natural size, 



Fig. 4. Petrosia similis, erect, lobose form ; natural size, 



Fig. 5. Petrosia similis, var. compacta ; natural size, 



Fig. 6. Petrosia similis, var. massa ; natural size, 



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