80 BULLETIN OF THE 



Eastern branch region is not specially rich in floral treasures, but 

 on its banks and marshes some good things appear. . Habenaria 

 virescens, Steironema laceolatum, Eleocharis quadrangulata, Scirpus 

 fluviatilis, Ranunculus ambigens, and Salix Russelliana are among 

 these, though some of them are found elsewhere. 



Flowering time of Plants. 



It has already been remarked that most species flower at Wash- 

 ington much earlier than at points farther north or the dates given 

 in the manuals. In consequence of this, a botanist unacquainted 

 with this fact, and accustomed to those climates and to relying upon 

 the books, would be likely to be behind the season throughout the 

 year, and fail to get the greater part of the plants he desired. With 

 all my efforts to make allowance for this fact, I have frequently 

 been sorely disappointed and was at last driven to making a care- 

 ful record, preserving and correcting it from year to year, of the 

 flowering time of plants in this locality. The notes on this subject 

 appended to nearly every species enumerated in the list embody the 

 general results of these observations and may in the main be relied 

 upon. The expressions used are not loose conjectures, but are in 

 the nature of compilations from recorded data. In most cases an 

 allowance of two weeks may be made for the difference in seasons 

 though rarely more and often less. Certain plants, as for example, 

 Tipularia discolor, flower at almost exactly the same time every 

 year. Occasionally, however, one will vary a month or more in a 

 quite unaccountable way. But any one who has watched the peri- 

 odical changes of the general vegetation for a series of years and 

 recorded his observations, will more and more realize the exactness 

 even of these complex biological phenomena which depend so abso- 

 lutely upon uniform astronomical events. 



From this point of view the season which presents the greatest 

 variation and also, for this and other reasons, the greatest interest 

 is the spring. There are a few plants which may sometimes be 

 found in flower here in January, such as Stellaria media, Taraxacum 

 dens-leonis or Acer dasycarpum (collected Jan. 17, 1876, in the 

 city) in favored places, but these will bloom at any time when a 

 few days of mild weather with sunshine can come to revive them. 

 There are, however, several strictly vernal species which bloom quite 

 regularly in the latter part of February, such as Symplocarpus foe- 



