486 
F. L. PICKETT 
produce proliferations — sometimevS mistaken for apogamous sporo- 
phytes — from unusually active cells of the surface. As described by 
Goebel (I: 49), prothallia of Osmunda regalis when old may produce 
branches from the older meristematic region. The outgrowths of 
Camptosorus do no t righ tly belong to either of these groups. They were 
first described briefly by the writer in the Botanical Gazette of March, 
1 9 14. In old prothallia which have been subjected to long periods 
of drought, the older portions die away leaving groups of living 
marginal cells, or limited living areas below the margin. The older 
portions after they are no longer vegetatively active, conduct water to 
the active cell groups for a time. Some of the outgrowths are small, 
irregular, without apical cell or group and are but one cell in thickness. 
These bear rhizoids, and an abundance of antheridia but no archegonia. 
Others soon show apical groups, develop typical prothallial forms and 
produce rhizoids, meristematic cushions and both antheridia and 
archegonia. In short, these marginal proliferations show all the char- 
acteristics of normal prothallia, and after a time, through the breaking 
down of the tissue of the original plate, become entirely independent. 
Their sex organs are normal, and they produce sporophytes abun- 
dantly, sometimes while yet attached to the old prothallial mass. 
While they are found most abundantly on plants which have been 
subjected to unfavorable conditions, their formation is not wholly 
dependent upon such conditions, as evidenced by the fact that on some 
plants the marginal activity has proceeded far enough for independent 
growth by the time the first archegonia have died. The number of 
proliferations varies. Usually but two or three reach any considerable 
size, but in other cases as high as fifteen such independent growths 
have been counted. Fig. 38 shows a plant with rather unusual 
marginal development. In this figure Q shows the oldest portion of 
archegonial meristem, from which yet older dead tissue has broken 
away. In the irregular growth of the plant this cushion has taken a 
curved form, and its latest development is at 0 where a sporophyte 
has appeared. At points ^ to marginal growth has produced pro- 
liferations. P was attached at point T and broken away in preparing 
the specimen for photographing. The dark central area and much of 
the lighter area around it are dead tissue. The root of a young sporo- 
phyte is shown at 5 and the leaf and stem buds at 0. The first leaf 
was broken ofif in mounting. The mottled mass just behind the 
sporophyte at 0 shows the region of numerous antheridia and arche- 
