THE PLANT WOELD 243 



Although a greater variety of species is usually to be found in moist 

 or protected situations, the bleak, exposed places should not be passed by, 

 for many of the most interesting forms occur there. One can hardly go 

 out for a walk anywhere without finding a place where lichens flourish. 

 Some years since, while the writer was walking along the street in Cam- 

 bridge, Mass., a chance exomination of an elm tree growing by the walk 

 revealed a very rare Rinodina, in great quantity. The species had been 

 reported but once or twice since its original description by the lamented 

 Professor Tuckerman. 



FOSSIL MOSSES, 



BY F. H. KNOWLTON. 



I HAVE been requested to prepare an article on the subject of fossil 

 mosses, and I take this occasion to present the following somewhat 



hasty summary of the present state of our knowledge of the geo- 

 logical history of this interesting group of plants. It goes without say- 

 ing that the great majority of living mosses are of such small size and 

 relatively simple cellular structure, that only exceptional conditions 

 could result in their becoming fossilized, and inasmuch as the group 

 has always, so far as we know, occupied an eqally humble position in 

 the plant world, the further back we go in geologic time the greater 

 become the difliculties, and less and less likely the probability of their 

 being recognizedly preserved. In the absence of the characteristic moss 

 " fruit " or sporostegium, it is almost impossible to recognize fossil 

 moss-plant fragments. Yet it is not at all improbable that the group 

 was of early introduction and has been lost or obscured in the vicissi- 

 tudes of rock deposition and transformation. Limpricht has expressed 

 the opinion that mosses played an exceedingly important role in past 

 time, and, while we have no very direct proof of this, it is not, perhaps, 

 impossible. 



A number of forms have been described from the Coal-Measures, 

 that present very much the appearance of mosses, but they are without 

 " fruit " and must be held to be more or less questionable. On the other 

 hand there are Palaeozoic specimens that have been described as twigs 

 of Lycopodites, Selaginites or Lepidodendron, that may have been por- 

 tions of mosses, and there are certain supposed conifers with small and 

 crowded scale leaves that are not unlike some of the stouter forms of 

 moss stems. Solms-Laubach has suggested that some of the small 

 twigs described by Lesquereux as Lycopodites Meeki, from our Coal- 

 Measures, may possibly belong to a moss, but Seward inclines to 



