XXXVIII] PTERIS 55 



represented only by its stalk, lies at the centre of the receptacle, while the 

 later sporangia right and left show the "mixed" condition of the sorus fully 

 established. 



Anopteris hexagoiia L., C. Chr. { = Pieris heterophylla L.) has been brought into promi- 

 nence by Mettenius in relation to his theory of connation of hairs ( Verwachsung) to form 

 the lower indusium. He stated that the "paraphyses" are disposed in a series along the 

 inner limit of the sorus, and are so closely ranged that they seem to form an indusium, 

 which grows out distally into hairs projecting as cilia upon its margin. He concludes that 

 the inner indusium, such as is seen in Pteridium, has arisen by fusion of hairs like those 

 oi A?iopteris {Far/igatiungen, Frankfurt, 1858). It has been found in sections cut vertically 

 through the young sorus of this Fern that the hairs are very numerous, but never webbed ; 

 the sporangia are relatively few. The first hairs originate in no definite relation to the 



V-/ 



Fig. 619. A, i) =vertical sections through young sori of Pteris serridata L. fil. ( x 150.) The 

 indusium is liere a direct continuation of the marginal growth, and the flattened receptacle and 

 sporangia arise from the lower surface. C=a similar section through a nearly mature sorus of 

 Pteris cretica L. ( x 75.) 



inner limit of the receptacle, where theoretically the inner indusium should be ; later the 

 whole width of the receptacle may be occupied by them. These facts are quite out of 

 harmony with Mettenius' theory, which itself does not accord with the facts and com- 

 parisons detailed above for other Pteroid Ferns. Such hairs as are seen in the sorus of 

 Anopteris may be held simply as paraphyses scattered over the receptacle, as they are in 

 other species oS. Pteris; though here they are more closely arranged than usual. (See 

 Studies VII, 1918, p. 41, Fig. 30.) 



Comparing the mode of origin of the sorus thus described for Pteris with 

 that seen in the Dicksonioid Ferns, or at nearer hand with that in bi-indusiate 

 types such as Lmdsaya, Pteridiian or Paesia, the differences are (i) that in 

 Pteris there is no lower indusium, (ii) that the upper indusium is actually 

 marginal in its origin, appearing as a direct continuation of the marginal 

 segmentation of the blade ; (iii) that the sporangia arise superficially from the 



