620 BLAcK: BRANCHED CELLS IN ONOCLEA SENSIBILIS L. 
2. The production of an irregularly lobed apical cell (Fics. 
2,°8, 9). 
3. An individual cell in the filament may develop an outgrowth 
or branch without forming a cross wall at the base (Fics. 6,7, 10).° 
4. A branched filamentous prothallium may have the pro- 
liferations originating in one cell (Fics. 7, 10, 11). 
5. An increase in the number of growing regions. (FIGS. 3-11). 
An exact knowledge of the optimum physiological conditions 
under which fern prothallia will grow and the changes that occur 
when this condition is modified would be of interest since the fern 
gametophyte has shown itself to possess great potentiality. 
New HAMPSHIRE COLLEGE, 
DuRHAM, NEW HAMPSHIRE 
LITERATURE CITED 
. Pickett, F. L. The development of the prothallium of Camptosorus 
rhizophyllus. Bot. Gaz. 57: 228-238. pl. 12, 13. 14 
. Pickett, F. L. Resistance of the prothallia of Camptosorus rhizo- 
phyllus to desiccation. Bull. Torrey Club 40: 641-645. I913- 
Wuist, Elizabeth Dorothy. The physiological conditions for the 
development of monoecious prothallia in Onoclea Struthiopteris. 
Bot. Gaz. 49: 1910. 216-219. 1910. 
_ 
N 
a 
a 
Struthiopteris. Bot. Gaz. 50: 209-213. I910. 
. Pace, Lula. Some peculiar fern prothallia. Bot. Gaz. 50: 49-58. 
on 
1910. 
. Goebel, KK. Organography of plants. Englishtrans. Oxford. 1905- 
ON 
Explanation of plates 22 and 23 
All the figures were drawn with the aid of a camera lucida. 
Fic. 1. Normal prothallium from the surface of culture showing typical form 
with a well-defined apical region. 
Fic. A five-celled prothallium with an unusually long apical cell, swollen at 
the end, which i is turned, indicating an abrupt change in the direction of growth. 
Fic. 3. The end of the filament forms an acute angle with the main cell thread. 
Fic. 4. A small cell cut off from the apical cell is growing in the opposite direc- 
tion. 
Fic. 5. A normal gametophyte with the possibility of two growing points 
1G.6. An extreme case of branched cells; two cells have well-defined pro- 
Fic. 7. Two filaments originating in a two-armed cell. 
Fics. 8,9. Irregularly lobed apical cells 
Fic. 10. A two-armed prothallium due to the branching of one cell. 
Fic. 11. Three branches originating in one cell. 
. Mottier, David M. Notes on the sex of the gametophyte of Onoclea 
eS ek ata a 
Pa ee ee 
i a et 
