PTERIDOPH YTES—FI LIC ALES 
257 
quently, the bud contains young leaves of three successive seasons. 
Two of the three show a differentiation into sterile and fertile portions. 
In Osmunda, and in many other ferns of similar habit, the 
rhizome is surrounded by the very hard leaf bases. Good sections 
of the central cylinder can be secured only by dissecting away these 
hard leaf bases and any hard portions of the cortex before attempting 
to cut sections. A short dis¬ 
tance back of the growing 
point will be found a region 
which will show practically all 
the structures of the mature 
stem, which will be easy to 
cut. Even in this region the 
leaf bases should be dissected 
away. From the apical cell 
back to the region where the 
sclerenchyma is beginning to 
turn brown, the material is 
easily cut in paraffin. Older 
portions should be cut free¬ 
hand. Osmunda affords an 
excellent illustration of the 
mesarch siphonostele (Fig. 83). 
The rhizome of Adiantum 
affords a good illustration of 
leaf gap and leaf trace. The 
vascular cylinder is a mesarch 
siphonostele; but there are few 
sections like Figure 81, because 
the clyinder is so interrupted 
by leaf gaps. This rhizome 
cuts well without imbedding. The petiole of Botrychium , in trans¬ 
verse sections below the fertile spike, shows the interesting leaf-trace 
situation which proves that the fertile spike consists of a pair of 
pinnae fused together. 
The ferns of the Gray’s Manual range afford no very satisfactory 
material for illustrating the protostele, although protosteles occur 
in Lygodium and Trichomanes. The most satisfactory material is 
Gleichenia, a very common and very beautiful fern in tropical and 
Fig. 83 .—Osmunda cinnamomea: photomicro¬ 
graph of single bundle of the mesarch siphonostele. 
Stained in safranin and anilin blue. Eastman Com¬ 
mercial Ortho film, Wratten C (blue-violet) filter; 
Bausch and Lomb 4-mm. objective, N.A. .65; ex¬ 
posure, 4 seconds. Negative by Dr. P. J. Sedg¬ 
wick. X108. 
