PTERIDOPHYTES—FILICALES 
265 
ranean and tuberous and, besides, looks so much like the root that 
you may not recognize it, even when you have it in your hand. 
The Embryo. —Instructive mounts of the whole embryo, with the 
pro thallium still attached can be made by the Venetian turpentine 
method. Iron-alum haematoxylin, with the stain not too deep, 
Fig. 90. — Osmunda cinnamomea: 
photomicrograph of vertical section of 
prothallium with an early stage in the de¬ 
velopment of the archegonium, showing the 
basal cell, two neck cells, and, between 
them, the cell which is to give rise to the 
neck canal cell, the ventral canal cell, and 
the egg—chromo-acetic acid; safranin, 
gentian-violet; from a preparation by Dr. 
W. J. G. Land. Negative by Miss Ethel 
Thomas. X425. 
Fig. 91. —Osmunda cinnamomea: 
photomicrograph of a vertical section with 
a young archegonium, showing the neck 
canal cell with two nuclei, the ventral 
canal cell, the egg, and the basal cell— 
chromo-acetic acid; safranin, gentian- 
violet; from a preparation by Dr. W. J. G. 
Land. Negative by Miss Ethel Thomas 
X293. 
is good; Magdala red and anilin blue are more transparent and will 
show the structure of the root, if the two stains are well balanced. 
For sections, cut longitudinally, perpendicular to the prothallium. 
Pteris longifolia may show the young embryo within 3 or 4 weeks; 
Osmunda , somewhat later. 
