178 THE PATHOLOUY OF POLLEN IN .ESTIVLS, 



the stigma at the top is charged with a saccharine, sticky mucilage. 

 A pollen-grain, borne by the wind, or an insect, usually, now falls 

 upon the stigma, and is anchored to it by the spines sinking into 

 the gum. The moisture causes the grain to swell. There is a 

 protrusion of the membrane at one or more of the thin places at 

 the surface, whence a tube, or root-like process, emerges, and 

 penetrates the stigma. It seems to be an extension in tubular 

 fwrm of the membrane, and is filled with the protoplasm of the cell. 

 If tlie kid-glove on a lady's hand could be pinched at the back, 

 and that nip of the glove pulled out or extended, and the flesh 

 could flow into this extemporised little pipe, it would roughly 

 represent the pollen tube. Having pierced the outer coat of the 

 stigma, this tubule, by a sort of growth, keeps on lengthening, and 

 pushing its way down through the loose tissue of the style, until it 

 has reached the ovule at the base, when its mission ends, and the 

 future seed of that flower is assured. 



Now to return to my statement of mistaken instinct in the 

 insect. Pseudo -instinct is also found in plants, even in the initial 

 life-processes. The surcharged nectary of a flower may appear in 

 a place aoproachable to a pollen grain. Should the granule alight 

 upon that viscid spot, out would pop the pollen-tube, with the 

 usual effort to pierce the epidermis of the flower, but in vain. 

 Indeed, we can easily deceive the pollen-grain, by dropping it upon 

 moistened sugar, and even witness this out-put of the tubule. 



The point I would now make is this — that a similar pseudo- 

 instinct prevails with the pollen-grain, when it is inhaled, and falls 

 upon the moist and tender tissues of the inflamed linings of the 

 respiratory passages. All the favouring conditions are there — mois- 

 ture, softness, and warmth. Hence results an instinctive protrusion 

 of the pollen-tube into the puffy, inflamed, and exquisitely sensitive 

 tissues. I think this parasitical action has to do with that acute 

 stinging sensation in the nostrils so frequent in ^^stivis. 



Thus have been instanced four possible modes of action for 

 pollen in Hay-Fever. 



I. — Its suffocating effect as an impurity of the atmosphere, 

 thus exciting asthma. 



2. — As a mechanical irritant begetting inflammation, even to 

 excoriation of the mucous membrane. 



