l888.J NEW-YORK MICROSCOPICAL SOCIETY. 101 



pears. If now we pass a red-hot bar through it, the beam will 

 be divided into two parts by a black space. The bar withdrawn, 

 soon the neighboring motes dance into it, and the beam is all 

 light again. 



The deduction, for our purpose, is that the so-called im- 

 purities present are chiefly organic, and the heat burns them 

 out. The spores, infusoria, and microbic matter are thus 

 destroyed — the air literally being purified by fire. 



All these things, even the mineral matter constitute the aerial 

 dust so distressing to the sufferer from Hay-Fever. And I hold 

 that a prominent irritant in the air, during the Hay-Fever 

 season, is pollen. 



But what is pollen ? It is the fertilizing granule produced by 

 the stamens of a flower. These granules vary greatly in size 

 and form, in the different flowers. Some are smooth, others 

 are angular, but those, with which this discussion will deal, are 

 globular, or elliptical, spiny, and very minute. Not noticing the 

 pollen of the grasses, which particularly affect the early forms 

 of the disease, perhaps the most mischievous of the pollens are 

 those of the Rag-weed, and the Golden-rods. I have here speci- 

 mens of the plants ; Rag-weed, Ambrosia artemisicefolia, L., and 

 the Golden-rods, Solidago alttssima, L., S. lanceolata, L., and S. 

 squarrosa, Muhl., which three forms are typical. I have here 

 also, under these microscopes, pollen of all these plants, mounted 

 on slides ; also here are enlarged drawings of the pollens. 



Fresh Rag- weed pollen is very nearly spherical. The granule 

 measures in these specimens, which are a little distorted by 

 long drying, rhn inch in length by lim inch in width. In a 

 fresh specimen, or such as floats in the summer air, so fine are 

 the points of the spines that they are to that of a cambric needle, 

 as it is to the point of a marling-spike, or even a crow-bar. 

 And yet this object, with its subtle armature is literally invisible 

 to the unaided sight. See Fig. i. 



The pollen-grains of the Golden-rods are sub-elliptical, both 

 ends being of the same size. They are very spiny, and the 

 spines are relatively longer than those on the pollen of the Rag- 

 weed, They are of two lengths on the same granule. The 

 pollen of S. altissima, the most abundant, in these parts, of the 

 many species, is in length %i^ inch, and in width ttsW inch. 



