Maidenhair Spleenwort 73 
Asplenium trichomanes Linneus, Species Plantarum, 1080. 1753. 
Younc plants of Asplenium trichomanes are apt to be con- 
fused with those of A. platyneuron, but can be easily distinguished 
by the dark petioles of the very young leaves.* The petiole is 
partly or entirely green in the young plant’s first leaf, but becomes 
almost at once, in succeeding leaves, dark and lustrous, shading 
from stramineous-brown to dark purplish-brown. 
Narrow membranous wings on the sides of the petiole, and 
of the rachis if there is one, are visible from a very early stage of 
leaf-development, if not from the first. At first the leaf-blade is 
roundish-spatulate, and contains a simple vein. It then becomes 
spatulate and obscurely notched at apex, next obcordate, and 
then cuneate-bilobed; and the vein sends out two branches at 
apex, each occupying one of the lobes. The leaf-blade then be- 
comes slightly more complex, lobed, and crenate, and its primary 
vein (midvein) develops somewhat beyond the two first primary 
branches. 
The parts of the leaf-blade that contain these two basal primary 
branches then separate from the upper part of the leaf-blade 
sufficiently to form two pinne, while the part of the leaf-blade 
remaining above them that contains the section of the leaf’s 
primary midvein between the latter’s first (basal) and second 
pair of primary branches becomes elongate and attenuate, form- 
ing a rachis, over which the dark color of the leaf’s petiole spreads 
quickly. Additional pairs of pinne are added successively to the 
leaf in a similar way; by parts of the leaf containing the pair of 
primary branches of the leaf’s primary midvein, next above the 
last pair of pinne previously formed, separating from the upper 
part of the leaf sufficiently to form a pair of pinne, while the part 
* See page 71. 
