152 Campbell 1 — The Gametophyte and 
of the second leaf joins the primary strand of the cotyledon and root at 
a considerable distance below the level of the stem apex. 
The first tracheary tissue in the primary bundle is formed at a point 
a little above the point of junction with the trace from the second leaf. The 
primary tracheary tissue consists of a bundle of short reticulate tracheides. 
Text-fig. 8. From a microphotograph of a young sporophyte just before the emergence of 
the cotyledon, .r., suspensor ; ar archegonium. Photograph by Dr. H. L. Lvon. 
From this point the development of permanent tissue in the bundle proceeds 
upward into the petiole and downward into the root. Shortly after the 
formation of the first tracheary tissue in the primary bundle, tracheides 
appear at the base of the trace from the second leaf, where it joins the 
primary bundle, and from this point the formation extends upward. 
With the elongation of the cotyledon it soon breaks through the over- 
lying tissues of the gametophyte and emerges upon its dorsal side. Then, 
