/3o THE PLANT WORLD. 



have not before been found so far west, and four of them I consider 

 to be new. I trust that you will not blame me for naming the major- 

 ity after the discoverer." Mr. Rydberg-, when he prepared his report 

 on the Flora of the black Hills, was not aware that this interestintr 

 collection was within a mile of him or he would doubtless have re- 

 ferred to it. The plants, "especially those from the Black Hills, are 

 prepared with much care and are often accompanied by critical notes 

 of value, which shows that Dr. Forwood is a keen observer as well as 

 a painstaking- collector. Dr. Forwood's purpose in presenting his col- 

 lection to the National Herbarium is that it may be more accessible 

 to working botanists and receive better care than the migratory life 

 of an army oiiticer will permit. It is important to state that we have 

 a full set of Dr. Forwood's types, among which are the following, 

 named for him: Astragalus Forwoodii^ Artemisia Foriuoodii, Aster 

 Forwoodii, and Gentiana Forz^'oodii. — •/. N. Rose, U. S. National Mu- 

 seum., Washington, D. C. 



In the spring, and especially in early spring, in the vicinity of 

 Washington, it frequently happens that after a shower the edge of 

 every pool of water in the streets and along the sidewalks will be 

 bordered by a rim of pale yellow color. As the water evaporates this 

 ring remains as a fine powdery mass, so much resembling sulphur as to 

 have given rise to the popular name of sulphur showers. This so-called 

 sulphur is, of course, not really sulphur, but when examined under 

 I he microscope, is found to be made up of a mass of the yellowish 

 pollen grains of pine trees. Instead of consisting of a single cell, as 

 do most pollen grains, this consists of three cells, the two larger end 

 ones being filled with air and the other containing the ordinary fertil- 

 izing principle. The two air-containing cells are larger than the 

 other and act like balloons to buoy it up in the air. In the pines and 

 allied trees fertilization of the cones, by which they are enabled to set 

 and develop seeds, is accomplished by the wind. That is, the pollen 

 is produced in immense quantities and is transported through the air 

 to the cones, which are often on separate, widely distant trees. It thus 

 often happens that the pollen gets up in the higher currents of the 

 air, is carried for long distances, and is only brought down to the 

 earth by the rain, producing the so-called shower of sulphur. A 

 shower of this kind occurred in Washington in March, iS86, and was 

 sufficient in amount to be very noticeable. By careful investigation 

 it was concluded that no pine trees could possibly be in flower at that 

 particular season nearer than Alabama, Georgia and the Carolinas. 

 It was recalled that the rain had been preceded by a strong wind 

 from the south, which had borne the pollen for hundreds of miles 

 and precipitated or deposited it during the rain storm. — F. H. K. 



