407 
oped than in the lower orders of ferns would seem to favor the 
possibility of there being a primary unequal segmentation of the 
embryo. 
BOTANICAL DEPARTMENT, 
CORNELL UNIVERSITY. 
Two Perfectly Developed Embryos on a single Prothallium of 
Adiantum cuneatum, 
By Gro. F. ATKINSON. 
It is well known that several archegonia on a single prothallium 
of the ferns may possess fertilized eggs. In some cases more than 
one of them is known to begin embryological development, but it 
is quite rare that more than one becomes a perfectly developed 
embryo capable of forming an independent plant. The statement 
is sometimes made that while several archegonia may possess fer- 
tilized eggs never more than one embryo is perfectly developed. 
Heinricher,* in lighting prothallia both above and below, suc- 
_ ceeded in causing the development of archegonia in numbers on 
both surfaces. In two cases two archegonia possessed fertilized 
€ggs which developed into perfect embryos, one each above and 
below. This might be considered an abnormal condition induced 
from the peculiar condition of lighting. 
Rauwenhoff+ notes the development of two embryos on 
Single prothallia of Gleichenia. In both of these cases, however, 
We are not informed of the comparative strength or advanced con- 
dition of growth of the embryos, so that it may be an open ques- 
tion whether both of the embryos on a single Pomiaihatn could 
have developed into independent plants. 
Campbell t also observes two embryos on a sttigle prothallium 
of Osmunda, but states that one was far in advance of the other, 
and would probably have starved it out before the two could ob- 
tain foothold i in the soil. : 
_  ™Heéinricher, Beeinnflusst das licht die Organ ‘hides am Farn Embryos, Mitt 
heilungen des bot. Inst. zu Graz, Heft IL, pp. 239-253. 
+ Rauwenhoff, De geslechtsgeneratie der Gleicheniaceen. Verh. d. tector 
Akad. van Wetensch. t. Amsterdam, 1889. 
__ $ Campbell, On the Prothallium and Embryo of Osmunda Claytoniana’ wet oO. 
ee Ann. Bot. iy 1892, 49-94. 
