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agrostis stolonifera, hieracium, pilosella, &c. &c. are 
equally familiar instances of plants which become 
social from their mode of propagation. But a more 
rare, and not less striking instance, is that of the 
willow grass, called Saule en herbe. Let us suppose 
the seed of a willow springing up at the foot of a 
mountain, and that the earth which is annually car- 
ried down by the rains from this mountain should 
be sufficient to bury the young plant. The follow- 
ing spring it would again shoot out with redoubled 
vigour ; for the growth of the plant having been 
checked by the fall of the soil, the sap, which should 
have been expended in the produce of foliage, being 
accumulated in the little stem, will be sufficient to 
afford nourishment for a double shoot ; two little 
branches will therefore now appear. This, like its 
predecessor, flourishes but for a season, and is bu- 
ried: the two stems the following spring produce 
four, which expand their leaves, and in the autumn 
are consigned to the earth; the third year eight 
stems arise ; the fourth, sixteen ; and the plant goes 
on thus doubling its sprouts every year, the surface 
of the soil rising, till at length a plain is formed, 
covered with verdure, consisting of the leaves of the 
willow tree 8. 
The rarity of some sea-shells seems to shew a less 
social habit in some species than in others. The 
dentalium is an example of solitude, living immersed 
in mud on shores rarely exposed to tempests. Se- 
y Mrs. Marcet’s Conversations on Vegetable Phys. 
