Igtt] CHARLES—ANATOMY OF MARATTIA Q7 
mucilage to stain changes rapidly and it takes the safranin. At 
this time and earlier than in Danaea the small cells begin to break 
down and the mucilage becomes stringy (fig. 41). The small cells do 
not break down uniformly; they may extend into the cavity of 
the duct as the “‘bridge-cells’’ of Danaea or float in the mucilage. 
The schizogenous stage may be omitted and cells of the pith break 
down into mucilage directly. Although tannin cells are numerous, 
none appeared to be changing to mucilage ducts as Lutz (20) 
describes for Angiopteris. The origin and development of the 
mucilage ducts in the seedling of Microcycas are identical with those 
of M. alata. 
Summary and conclusions 
1. The transition from protostele to solenostele in Marattia is 
sudden and without the intervention of a definite medullated 
monostelic stage. The indefinite hints of pith due to the early 
start of parenchyma to divide leaf trace from stele may be the origin 
of the medullated stage. 
2. The medullary system of Marattia differs from that of the 
solenostelic ferns in origin, course of bundles, and development into 
a cylinder. It resembles that of Psaronius in its relation to leaf 
traces. 
3. Elongation of the stem causes the union of the bundles into 
broad bands and a reduction of the medullary system. This 
emphasizes the close relation between the compact habit and 
crowded leaves of Marattia and the number of concentric cycles 
and leaf gaps in the dictyostele. The difference in habit, there- 
fore, accounts for the difference in the anatomy of Marattia 
and the more elongated Marattiaceae, Danaea, and Kaulfussia, 
and the treelike Psaronius. 
4. The occurrence and position of protoxylem varies. It may 
not be distinguishable or may consist of spiral or modified reticulate 
tracheids. When distinguishable, it may be in an exarch or 
mesarch position in the cotyledonary node, mesarch in the pro- 
tostele above the cotyledonary node, and usually endarch in the 
strands of the older parts of the stem. Similar variations occur 
in the leaf traces. The cotyledonary trace may change from 
