POLLINGS IS 43 



the mechanisiii by which pollen-j^roteid can come into contact with 

 the nasal mucosa, the cell-contents may be dismissed from the role of 

 active agent. It remains to consider : — 



(1) The question of the mere mechanical irritation, due to the 



presence of a foreign body, being sufficient to cause the 

 symptoms. 



(2) The possibility of some substance on the outer wall (exine) of 



the grain being responsible. 



In answer to the first question, it may be said that the presence 

 of foreign bodies on an otherwise undamaged mucous membrane may 

 produce transient sneezing and secretion, but nothing like a real 

 paroxysm. Of course, where the foreign bod}'- is atmosplieric dust, 

 which may contain j)articles of alien protein, grit, etc., the irritation 

 may be more pronounced ; and such irritation, or even the action of 

 cold air, superimposed upon a previous catarrhal condition, may, as 

 mentioned before, produce effects very similar to a primary hay-fever 

 attack. The second point is more difficult and more important. The 

 microspores of Angiosperms and GymnosperuLs are formed in tetrads 

 within the microsporangium, which is lined by a nutritive tapetum. 

 This tapetal layer furnishes food-material for the developing spores, 

 but disorganizes before they are shed. Consequently the pollen- 

 grains are coated on the outside, as is seen in the yellow colour, by 

 tapetal debris, which may be almost anything (commonly oily matter), 

 and in which it is conceivable that protein and enzyme-residues may 

 be present in minute quantities. The yellow colour of manj^ pollen- 

 grains is in all cases outside the cuticle, and consists of carotin 

 dissolved in a film of oil. The function of this oil is conjectural, but 

 it may conceivably assist in sealing the grain still better, protecting 

 it from excessive wetting, and preventing the grains from adhering- 

 (^cf. the curious way in \\\\\q\\ Finns pollen "pours"). From analogy 

 with the well-known irritant oils in Primula obconica, P. sinensis, 

 etc., it seemed probable that this oily film on the pollen-grains was 

 the irritant principle, and experiments were undertaken to demonstrate 

 this, but the results are not yet collected. For example, a suggestive 

 preliminar}^ trial was made with the pollen of Hihiscvs. The pollen 

 was shaken up with cold ether, the ether then being filtered oft" and 

 allowed to evaporate. The oily residue, when applied to the unbroken 

 skin of the fore-arm, raised a severe blister, almost as bad as that 

 produced By Poison Iv}" {Rhns Toxicodendron). 



This would seem to indicate a more natural method of approaching 

 the problem, being based upon a botanical consideration of the micro- 

 spores involved. It is quite possible that most microspores are coated 

 with a him of oil, but only a certain number of pollens are produced 

 in sufficiently large quantities to be of any practical importance. 

 This includes the wind-pollinated trees, both Angiosperms and Gym- 

 nosperms, and the Grasses, particularly the common hay-grasses. 

 Species of Plantar/o also give much pollen, and a laboratory trial 

 with PIantago-\^o\\(i\\ alone gave a positive result. If this idea that 

 one of the poisonous principles of pollen is merely that of an irritant 

 oil is correct, it will throw a new light on the nature of the dama^j-e 



