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AMERICAN FORESTRY 



family (Pontederiaceae) contains but one other plant be- 

 sides the true pickerel weed, and that is the mud plantain 

 (Heteranthera renifonnis), which bears but very slight 

 resemblance to the former. 



The story of the very essential cross-fertilization of 

 the flowers of the pickerel weed reads, as we often say, 



A GLIMPSE OF THE HISTORIC POTOMAC 



View from the Maryland side of tlie river, below Great Falls. On the hank 

 in the foreground is seen growing both Broad-leaved Arrowhead ISagit- 

 tana latifolia) and Pickerel Weed (Pontederia cordata). The trees here 

 shown are upon a small island, where, in days gone by, a pair or two of 

 turkey buzzards used to breed. 



like a fairy tale. It seems that there are three kinds of 

 blossoms on the spike, "one raises its stigma on a long 

 style reaching to the top of the flower," says Nellje 

 Blanchan in her excellent account of it ; "a second form 

 lifts its stigma only half way up, and the third keeps its 

 stigma in the bottom of the tube. Now there are two 

 sets of stamens, three in each set, bearing pollen grains 

 of different size and value. Whenever the stigma is 

 high, the two sets of stamens keep out of its way by oc- . 

 cupying the lowest and middle positions, or just where 



the stigmas occur in the two other forms ; or let us say, 

 whenever the stigma is in one of the three positions, the 

 different sets of stamens occupy the other two. In a long 

 series of experiments on flowers occurring in two or 

 three forms dimorphic and trimorphic Darwin proved 

 that perfect fertility can be obtained only when the 

 stigma in each form is pollenized with grains carried 

 from the stamens of a corresponding height. For exam- 

 |)le, a bee, on entering the flower, must get his abdomen 

 dusted with pollen from the long stamens, his chest cov- 

 ered from the middle length stamens, and his tongue 

 and chin from the set in the bottom of the tube nearest 

 the nectary. When he flies off to visit another flower, 

 these parts of his body, coming in contact with the stig- 

 mas that occupy precisely the position where the stamens 

 were in other individuals, he necessarily brushes off each 

 lot of pollen just where it will do the most good. Pollen 

 brought from high stamens, for example, to a low stig- 

 ma, even should it reach it, which is scarcely likely, takes 

 little or no effect." As pointed out, cross-fertilization is 

 extremely essential, and in these "three-formed flowers 

 there are two chances to one of securing it." Darwin 



A FAMOUS PLANT OF THE SWAMPS AND RIVER BANKS 



This is a beautiful specimen of the Pickerel Weed, the spike on either 

 hand being in full bloom, while the center one has gone to seed. So lux- 

 uriantly does this plant grow in some rivers that it has greatly interfered 

 with navigation, and special means have been recently devised in order to 

 clear the usual shipping tracks of it. Three forms of Pickerel Weed are 

 described, that is, different flowers on different plants, and the whole 

 group depend entirely upon visiting insects for fertilization. In late sum- 

 mer, when creeks, swamps, and ponds dry up, the Pickerel weeds turn 

 brown, wither, and die, and frequently the seeds are lost in the dry mud 

 wherein the sorry plant now finds itself. 



