XLV] 



CHEIROPLEURIA 



203 



periphery. The ring very soon opens out by an adaxial fission, the margins 

 withdrawing till the whole leaf-trace takes the form of a crescent, as in 

 Matonia and Dipteris. But in Cheiropleurm the trace is narrower, and the 

 protoxylems only two. Later the trace itself divides into two equal strands, 

 and so passes out into the petiole (Fig. 713). 



A B 



.. J =a transverse section of a protostele of Cheiropleuria showing a leaf-trace being given 



r^t rx i- t /?-a similar section, with the leaf-trace completely separated. It has two 



Lt^ .fouos with the met^xylem surrounding them completely-a condUion which 



Fig 



off from _ , ,^ , 



internal protoxylem groups, with the metaxyle 



holds only for a short distance. ( x 30) 



*.^ 1^ 



^ 



Ficr 713. Transverse section of the rhizome of Cheiropleuria, 

 lothow the relations of the leaf-trace and of the lateral bud to 

 the stele of the axis, a shows the relation of two normal leat- 

 traces, where no bud is formed, b—e show successive sections 

 from below upwards, in the case of a leaf-trace where a lateral 

 bud is borne on the abaxial side of it. ( x 3.) 



It is most unusual, in a Fern of relatively robust habit, and of so advanced 

 a type as Cheiropleuria proves to be, that the protostelic state should be 

 continued from the sporeling to the adult state (as in Gleichenia\ without 

 solenosteHc or other expansion : also that the origin of the leaf-trace should 



