31 



to the above species, one necessarily approaches the study of 

 related species with similar thoughts in mind. 



Two plants closely related to the common arrow-head were 

 separated in 1894 by Mr. Jared G. Smith in his revision of the 

 North American species of the genus. All the standard manu- 

 als since that time have recognized these two plants as valid spe- 

 cies, and the distinctness of Sagittaria Engelmaimiana J. G. 

 Smith and Sagittaria longir-ostra (Micheli) J. G. Smith, as these 

 two plants were named, has not been questioned. They are, of 

 course, both thoroughly distinct from Sagittaria latifolia, but 

 when one comes to study the distinctions relied on between the 

 two plants themselves, he soon finds out that the distinctions 

 emphasized are the very ones which are universally agreed to be 

 of no value in separating forms of Sagittaria latifolia. 



Thus Mr. Smith's own key is as follows : 



" Fertile pedicels much shorter than the bracts ; leaves ample; beak of the achenium 

 stout, erect R. longirostra 



" Fertile pedicels longer than the bracts ; leaves with linear lobes ; beak of the 

 achenium erect S. Kngelmanniana ' ' 



Practically the same key is used in the Illustrated Flora except 

 that the achenium characters are omitted, and properly so, be- 

 cause in Mr. Smith's detailed description he says that S. Engel- 

 manniana has a stout beak, thus leaving no marks of difference 

 in this respect. 



In the recently issued " Gray's Manual" the key used is 



"Stout; leaf-blades broadly ovate-oblong 5. longirostra 



"Slender; leaf-blades linear , S. Engelma777iiana'''' 



So much then for the history of the plants, and now for an 

 experience of my own with them. Although I had collected 

 the plants before this year, the collections never had been under 

 the most favorable conditions, but this year conditions seemed to 

 be just right, when on Labor Day I went to Forked River in the 

 New Jersey pine-barrens. Immediately beyond the station there, 

 there is an artificial pond, the shores and shallower portions of 

 which I quickly found were lined with Sagittaria. It was in 

 fine fruiting condition and many specimens agreed well with vS. 

 Engehnanniana as described in the manuals, but others had 



