S4 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



through a mediuna like air that offers but little 

 resistance. The narrow elongated body of a snake, 

 eel, or worm, on the other hand, is more convenient 

 for an animal which has to make its way between 

 the stems of reeds, or through a much-resisting 

 medium like the soil. To keep a bird in a cage is 

 a very simple matter, but a worm or a serpent 

 would easily escape. Elongated, and especially 

 aristate, seeds have the same advantage as the 

 snake in the cage — they can effect their passage 

 through narrow openings, as between matted grass- 

 stems which cover the soil with a network impene- 

 trable to winged seeds and fruits. For this reason 

 in a hay-loft the seeds always accumulate on the 

 floor, affording a fresh illustration of the proverbial 

 difficulty of finding a needle in a hay-stack. Pene- 

 tration is favoured by the presence of an awn-like 

 appendage, by a barbed or scabrid surface, and by 

 a fusiform shape. Reverting for a moment to the 

 analogy between the dispersion of seeds and the 

 postal system, dissemination may be said to involve 

 three distinct processes, viz., despatch, transport, 

 and delivery. Despatch is mostly effected by hygro- 

 scopic action, as in the opening of seed-capsules, the 

 explosive dehiscence of the anthers in Urtica and 

 Parietaria, the spreading of the pappus -hairs in 

 Carduus, etc. Other contrivances for facilitating 

 despatch are seen in the long filaments of grasses, 

 Plantago, Thalictrum, etc.; in the pendulous catkins 

 of Quercus; and in the slender pedicels of Rumex 

 and Briza. During the flowering period the stalk 

 of Tussilago, as we have seen, is erect. It curves 

 over after fertilisation, and remains with the capitu- 

 lum inverted until the fruits are ripe, when it again 

 becomes erect for the purpose of exposing the 

 plumed seeds to the wind. These and similar con- 

 trivances for despatch, might be compared to the 

 mail-bags hung up from signal-posts on our railway 

 lines from which the express train sweeps them off 

 into the net as it rushes past. Contrivances for 



