no 



plicity. Like wind pollinated flowers they have suffered reduc- 

 tions in response to anemophily. The grains of the grasses which 

 are all anemophilous are smooth and globular, ellipsoidal, or 

 ovoidal. Those of all species are very much alike, differing main- 

 ly in size. They may always be recognized by their thin outer 

 coat and single small germ pore slightly raised and provided 

 with a small operculum. The grains of English plantain are 

 somewhat similar but are provided with 7 to 14 pores and their 

 outer coat is slightly mottled. The grains of Rugel's plantain 

 are sometimes caught on pollen slides too, but may easily be 

 distinguished by their rougher coat and fewer pores, 6 to 10 

 in Rugel's and 4 to 6 in common plantain. The pollen grains of 

 birch are likewise smooth, generally provided with three pores 

 arranged around the equator, each elevated above the surface 

 so as to give the grain a triangular outline. The pollen grains 

 of all the birch family are like this. These grains, though simple, 

 are not primitive; they have achieved this simplicity by evolving 

 away from the central basic forms of angiospermous pollen 

 grains. In reverting to the primitive gymnospermous habit of 

 anemophily they tend to assume in some respects the gymno- 

 spermous simplicity of form, yet they can nearly always be 

 distinguished from them. We are reminded in this of the whales 

 and porpoises; upon returning to their remotely ancestral aquat- 

 ic habit they assumed in part the outward form of their fishy 

 ancestors but retained all the more important anatomical fea- 

 tures of their less remote mammalian ancestors. 



The goldenrod pollen grain may be taken as an example of 

 the basic form of those of the higher dicotyledons. It is a small 

 globular body about 23yu in diameter with a thin elastic but 

 unperforated inner coat and a thick semi-rigid outer coat, quite 

 appropriately likened to the inner tube and outer casing of an 

 automobile tire, and, like the latter, the outer coat of the pollen 

 grains of different plants exhibit an enormous variety of sculp- 

 turing, which is extremely convenient in enabling one to tell 

 which plant was responsible for their genesis. In the golden rod 

 pollen grain the outer coat is covered with short but sharp- 

 pointed conical spines. Since these grains are designed to be 

 carried by insects it might be assumed that these are "non-skid" 

 spines, so to speak, which help to keep the grains from slipping 

 off the insects. This may be partly their function, but under the 



