CONTROL OF THE SEXUAL STATE IN ARISAEMA TRIPHYLLUM 
AND ARISAEMA DRACONTIUM i 
John H. Schaffner 
(Received for publication June 2, 1921) 
Arisaema triphyllum (L.) Torr., being a dioecious plant with a con- 
siderable percentage of intermediate individuals, presented itself to the 
writer's mind as a very favorable plant for experiments on the control of 
sex, such experimental control seeming to be necessary to substantiate con- 
clusions reached previously, mainly from taxonomic studies, as to the fun- 
damental nature of the sexual state. Accordingly, work was begun on this 
plant in the spring of 191 7. More recently work has also been done on 
Arisaema Dracontium (L.) Schott. 
The first plantings were made in pots and were not very satisfactory, 
probably because there was no place in the greenhouse to keep them prop- 
erly, and the writer was absent during the entire winter. However, one 
pure carpellate plant changed to a pure staminate plant, and some inter- 
mediate individuals also changed to the staminate condition. The writer 
was certain, therefore, that sex reversal took place, and the results so far 
as they went agreed with the reports of sex reversal in Arisaema by Atkinson 
(i), Gow (2), and Pickett (3). The study was continued by observations 
in the field and by experiments in garden plots. 
Field Observations 
The individuals in the field are pure staminate, pure carpellate, or in- 
termediate in varying degrees from nearly pure staminate or carpellate 
to individuals having inflorescences with about an equal number of staminate 
and carpellate flowers. There are usually about 60 to 80 flowers on a 
fairly large inflorescence. The folding of the margins of the spathes appears 
to be an ordinary fluctuation. There are about equal numbers folded 
clockwise and contra-clockwise. The same conditions hold for the spathes 
of Arisaema Dracontium. 
As stated, the intermediate plants show all degrees of sexual expression. 
The inflorescence may be carpellate except for one imperfect or perfect 
staminate flower, or it may be staminate with a single carpellate flower, or 
from such a condition up through all gradations to a monoecious inflorescence 
with about an equal number of both kinds of flowers. There is no definite 
position for the appearance of the opposite type of flowers. Pickett (3) 
^ Papers from the Department of Botany, The Ohio State University, no. 130. 
72 
