236 Evans: Air chambers of Grimaldia fragrans 



Ricciocarpus, Peltolepis, Sauteria, Clevea, Plagiochasma, Reboulia, 

 Grimaldia, Neesiella, Cryptomitrium, Asterella and Bucegia; while 

 the Marchantia type occurs in Corsinia, Targionia, Conocephalum, 

 Lunularia, Preissia and Marchantia. The reduced air chambers 

 of CyatJwdium conform best perhaps to the Marchantia type, in 

 spite of the absence of green filaments, while the adult thallus of 

 Dumortiera lacks air chambers altogether. 



The genus Grimaldia Raddi, as understood by most recent 

 writers, contains about half a dozen species. The most widely 

 distributed of these is G. fragrans (Balb.) Corda, which is found in 

 Europe, Asia and North America. Other well-known species, 

 closely related to G. fragrans, are the Mediterranean G. dichotoma 

 Raddi and the Californian G. californica Gottsche. In the eastern 

 parts of the United States G. fragrans is sometimes locally abun- 

 dant, preferring sunny trap ridges and growing on earth among 

 rocks, rather than on the rocks themselves. It was in such a 

 locality as this, on West Rock Ridge, near New Haven, Connecti- 

 cut, that the material used in the present study was collected. 

 The narrow thallus is firm and compact and produces an abun- 

 dance of purple ventral scales with bleached-out appendages. 

 The upper surface is grayish green and shows no indications of the 

 boundaries of the air chambers beneath the epidermis. The 

 margins, as well as the ventral surface, are more or less pigmented 

 with purple. The species is markedly xerophytic, the margins 

 becoming involute when dry, thus covering over and protecting 

 the upper surface. 



The air chambers of the mature thallus 

 The green tissue of the thallus in Grimaldia has been repeatedly 

 described, most of the observations having been based on either 

 G. fragrans or G. dichotoma. Unfortunately the descriptions show 

 marked discrepancies. Stephani (ii), for example, states that 

 the air chambers are densely filled with erect green filaments 

 composed of long cylindrical cells, and K. Miiller (6, p. 259) 

 notes the presence of vertical plates of cells in addition to the 

 filaments. Schiffner (9, p. 309) criticizes these descriptions. 

 According to his account the chambers of Grimaldia undergo a 

 secondary partitioning by means of irregular green lamellae which 



