LASTREA. 135 



nearer the apex of the frond, become gradually less and less 

 compound, so that, although the margins are still furnished 

 with spinulose teeth, they gradually lose the deep lobes 

 which are found on the lowest pinnse. In all the more com- 

 pound Ferns there is a similar difference of form according 

 to the position of the pinnules, and in all such cases it is 

 usual to describe only those which are the most complete, 

 namely, such as are situated at the base of a few of the 

 lowermost pinnse. The stipes of Lastrea spinulosa is rather 

 sparingly furnished with semitransparent scales of a broad 

 or bluntly ovate form, in which particular it agrees with cris- 

 tata and uligintxa, but differs from dilatata an&famsecii. 



The venation of all these allied species is so very similar, 

 .that it is unnecessary to repeat the description in detail. In 

 the less divided pinnules there is a midrib, less tortuous 

 than in cristata, which gives off branched venules, the lower 

 anterior veinlets proceeding from which bear the sori, about 

 midway between the rib and the margin ; the clusters of 

 spore-cases thus forming an even double row on each pinnule. 

 "When the pinnule is more divided, the same arrangement 

 of the sori occurs on the lobes, the branches of the lateral 

 veins or venules being then more numerous. The sori are 

 covered by kidney-shaped indusia, having the margin entire. 



