DEVELOPMENT OF PLANTS 379 



flowers are perfect, containing one or several pistils that may 

 cohere and stamens which are surrounded by a very rudimentary 

 perianth. The relation of,,these plants to insects is a very inter- 

 esting one. The brigh^Jy colored spathe serves as an allurement 

 and it also protects the microspores against wetting. The spores 

 of comparatively few plants can endure water and it will be 

 interesting to observe in the following lessons the devices that 

 appear to guard against this danger. The spathe also affords 

 shelter to the insect and the temperature is higher within the 

 spathe since the food is being rapidly oxidized while the spores 

 are forming. The temperature of the larger spadices may ap- 

 proach blood heat, being 10 to 25 C. higher than the outside 

 air. Insects are not slow to avail themselves of these advantages 

 and they also find an abundance of food in the microspores and 

 glands that are often developed upon the spathe. Many aroids 

 are characterized by the foul odors of decaying flesh and it is 

 noteworthy that the coloration of the spathe is in singular har- 

 mony with these odors, resembling the hues of putrid meat. As 

 a result of these variations, the lower orders of insects visit these 

 flowers in great numbers and unwittingly serve in the transfer 

 of the microspores; 250 carrion beetles and over 1,000 midges 

 have been reported as taken from a single spathe. You can 

 readily demonstrate that small insects are attracted to the spathe 

 by examining the inflorescence of the skunk cabbage and jack- 

 in-the-pulpit. 



Common Examples of the Arales. In the skunk cabbage 

 (Spathyema foetida), which is of common occurrence along 

 muddy streams, the inflorescence may appear as early as Febru- 

 ary, while the leaves are still rolled up into a compact bodkin to 

 enable them to penetrate the soil. Later the leaves unroll and 

 become very large, being good types of aroid leaves with broad 

 blades, strongly net-veined and evidently adapted to abundant 

 moisture and rapid transpiration. The spathe is shell-like, mot- 

 tled with purple, green and yellow and encloses a fleshy oblong 

 spadix that is entirely covered with flowers. You will find that 

 small insects are attracted to these spathes in great numbers and 

 spiders often take advantage of this fact and spin their webs 



