24 Wisconsin Academy of Sciences, Arts, and Letters. 
The prothallium may live for a considerable time after 
the sporophyte has formed upon it. Apical growth, however, 
^ceases and the cells at the base of the apical notch grow to full 
size. The expansion of these cells makes the notch shallower 
-and pushes the lobes farther apart. Even after the prothallium 
estops growing, it may remain fresh and green until the spore- 
phyte borne upon it has five or six leaves and as many roots. 
5 The appearance upon a prothallium of an isolated member 
of the sporophyte, as a leaf or a root (so common in some apo- 
gamous ferns) is, so far as I have observed, rare in Aspidium 
falcatum. I have but once seen a leaf growing directly from 
the prothallium with no sign of stem apex or root. I have 
never seen an isolated root nor have I ever seen tracheids in the 
tissue of a prothallium which was producing no sporophyte. 
The mixtures of gametophytic and sporophytic characters which 
have been described by Lang and others for Scolopendrium 
vulgare and other ferns I have not found in Aspidium falca¬ 
tum. 
A certain percentage of the prothallia are slow to produce 
sporophytes or fail altogether to produce them. In these pro¬ 
thallia, the same growth phenomena are to be observed which 
are seen in old prothallia of normal ferns when an embryo is 
not formed. These prothallia of Aspidium falcatum continue 
growing for months and attain a length of two or three centi¬ 
meters. The growth may be apical, the prothallium becoming 
gradually narrower and thinner as it increases in length until 
it ends in a narrow one-layered strap of cells. Usually in this 
case the apical notch becomes very shallow and may even dis¬ 
appear. These conditions are doubtless due to unfavorable 
environment. 
Ordinarily, however, in prothallia producing no sporophyte, 
the growth is more irregular. Even in the prothallia described 
above, there is some marginal growth, resulting in notched edges 
and in more or less folding of the whole prothallium. Usually 
apical growth ceases entirely and marginal growth becomes more 
pronounced. Sometimes the two lobes grow out into broad 
straps. Sometimes growth begins at various points along the 
margin, the outgrowths varying greatly in width. An out- 
