POLLINATION AND FERTILIZATION 147 
numbers of gnats or midges are attracted to the flower cluster 
and do not easily find their way out of the chamber in which 
it is inclosed, but when they do escape, carry pollen with them 
to the next jack-in-the-pulpit which they visit, and pollinate 
the flowers there. 
The flower cluster 
of the common Euro- 
pean arum! has been 
so much more carefully 
studied than that of 
our related American 
plant, and is so much 
more successful in de- 
taining pollinating in- 
sects, that it is worth 
while to describe it in 
some detail. The cham- 
ber which surrounds Fre. 182. Pitfall flower clusters of the 
the flower cluster ap- European arum 
rately _4, exterior view of the flower cluster, about one 
pests to be mode J third natural size ; B, the same drawn to a larger 
open, and admits the scale, with part of the covering removed ; C, part 
free entrance and exit of B, drawn to still larger scale, with the flowers 
F more mature and the hairs (h) withering and al- 
of small insects. The lowing the escape of imprisoned midges; spad, 
spadiz. or floral axis. spadix, or floral axis; spathe, the hood covering 
i > the axis; 2, hairs closing narrowed part of spathe ; 
bears several rows stam, group of staminate flowers (not mature in 
of do ward-pointin: B, mature in (); pist, group of pistillate flowers 
‘ ie aa 8 Gust matured in B, pollinated and developing 
bristles (fig. 132, B). seeds in C). 1 and B, after H. Miller 
Small midges are at- 
tracted to the interior of the flower chamber by its peculiar 
ammonia-like smell and by its warmth, which is considerably 
greater than that of the outside air. The midges readily 
crawl down through the palisade hairs, often bringing with 
them pollen with which they have become dusted in other 
arum-flower clusters. As they crawl down the spadix they 
pass over the immature staminate flowers (fig. 182, B) and 
1 Arum maculatum. 
spad 
spathe 
