526 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9. 
It appears, then, that as the circumference of the young carpophore 
becomes greater the distance between the young lamellae at the margin 
becomes greater, and in the regions of the fundamental tissue and of the 
paHsade cells between these primordia of the lamellae, further differentiation 
of these tissues occurs which results in the formation of a new tramal plate 
bounded by palisade cells, which thus form a new gill — the short or secondary 
gill. The old gill cavity is split by the new gill. The apparent suspension 
of the secondary gill is due to the growth of the inner margin of this gill 
Diagrams 7-12. Top view of a series of carpophores showing the development of a 
secondary gill at "Z" by the development of a secondary gill cavity at " F." e' represents 
a region where the undifferentiated fundamental tissues of the stipe and pilear regions meet 
at the periphery of the carpophore; /, the increase in growth of the secondary gill. 
toward the stipe (see diagram 4), giving this edge a curved outline. Dia- 
grams 7 to 12 inclusive represent the development of a secondary gill. 
The letter a represents the undifferentiated region of the pilear structure, 
h the smooth palisade cells, c the oriented palisaded cells, d the young gills, 
and e the stipe region; e' represents a region where the undifferentiated 
fundamental tissue of the stipe and pilear regions, at the periphery of the 
carpophore, meet; / represents the increase in growth of the secondary gill. 
This series of diagrams shows a carpophore increasing gradually in size. 
With growth, the distance between the lamellae at 7, diagram 7, becomes 
greater, and more palisaded cells appear between the tramal elements as 
shown at x in diagram 8. A new center upon which the new palisade cells 
become oriented, at y in diagram 9, and a point z on the stipe fundament 
e\ become established with the differentiation of a new rudimentary trama, 
the hyphae of which are continuous between the stipe and the pilear regions. 
Continued growth upward into the pileus (diagram 10) makes the new 
