164 



GROWTH AND WORK OF PLANTS 



the lower part. The spadix is enclosed in a leaf-like structure, 

 forming a broad cylindrical tube (the " pulpit ") below, and above 

 tapering into a strap-shaped part (spathe) which bends forward 



over the pulpit. In some plants the 



!staminate and pistillate flowers are borne 

 on the same spadix (plants monoecious), 

 but usually they are all of one kind on a 

 spadix (plants dioecious). 

 271. A little observation will show 

 that the pistillate plants are the larger 

 and have larger corms, while the stam- 

 inate plants are smaller. The larger 

 corms have more stored food and thus 

 produce a larger aerial shoot. But why 

 they should produce pistillate flowers 

 is not so clear, though it probably 

 has some connection with the abun- 

 dant food supply. It is evident, how- 

 ever, that this is a useful distribution 

 of the flowers, since the pistillate flowers 

 produce the seed, which makes a greater 

 drain of food from the corm than the 

 mere production of stamens and pollen 

 would. Seed formation of the smaller 

 pistillate plants sometimes makes such 

 a drain of food from their smaller 

 corm, that the ensuing year they 

 change to staminate plants. In fact 

 the change from pistillate to staminate 

 plants can be demonstrated experi- 

 mentally, by removing the larger part 

 of the corm with a knife during late 

 summer or early autumn, before the nature of the flowers for 

 the coming year has been fixed. It follows from all these facts 

 that seedlings, or offsets from the corm, when they flower for the 

 first time probably bear staminate flowers. In a few years, if 



Fig. 124. 



Jack-in-the- pulpit or Indian 

 turnip (Arisaema triphyllum), 

 spathe removed, showing 

 spadix; the two upper figures 

 with pistillate flowers, lower 

 figures with staminate flowers. 



