April, 1922 SEXUAL nature of twins of aris.^ma 151 



study of a considerable number of twins of Arisaema, when it is 

 remembered that sex in Arisaema has nothing to do primarily 

 with chromosome shiftings and can be controlled and reversed 

 almost completely by environmental means. 



CHARACTERIZATION OF TYPICAL EXAMPLES. 



1. A plant with twin leaves on a common petiole and twdn 

 spadices on a common peduncle. The two leaves each had 

 three leaflets and had short petioles coming from the common 

 petiole. The spathe had tw^o points and surrounded the tw^o 

 spadices. Both spadices were pure carpellate and the sterile 

 tips both had the upper two-fifths colored dark purple. 



2. Twin shoots coming from the same corm. They were 

 alike in size and general appearance. Both had the sterile tip 

 purple. Both had identical sexual expression, being monecious 

 with a zone of carpellate flowers below, covering about three- 

 fifths of the spadix, and with a staminate zone above. Both 

 inflorescences had purple-red anthers and greenish white 

 stigmas. 



3. A pair of large twins with separate corms but evidently 

 just recently divided — probably the preceding summer. Both 

 were very late in coming out of the ground; both had green 

 spathes and green sterile tips; and both were pure carpellate 

 with violet stigmas. 



4. A pair of small twins with distinct corms but still close 

 together. Both had green spathes and green sterile tips. Both 

 were pure carpellate. One plant was 8 in. tall and the other 

 73^ in. 



5. Large separated twins, both 12 in. tall to the tip of the 

 spathe. The spathes of both were a uniform dark purple at the 

 tip on the inside, and purple and greenish-white striped below. 

 The sterile tips of both were dark purple above, purple spotted 

 in the middle part, and green below. The sterile narrow stalks 

 of the sterile tips were both purple spotted. Both were pure 

 carpellate with pale violet stigmas. 



6. A pair of twins just separated and situated close together. 

 Both were 6}/^ in. tall to the top of the sterile tip; both had one 

 larger and one smaller leaf; both had the spathes striped above, 

 broad purple stripes alternating with narrow greenish -white 

 stripes, and uniform greenish-white below. Both had the 



