By the Chevalier Francis de Paula Schrank. 399 



that have creeping roots (as Hydrocharis morsus-ramv, Meriy- 

 anthes Nymphoides, Menyanthes trifoliata) may enjoy a greater 

 depth of water. 



My account will be more perspicuous if I describe this 

 contrivance for aquatic plants as it has been executed in our 

 botanic garden. 



The garden has three large reservoirs of water (Fig. 1. A) 

 in each of which the level of the water is raised one foot 

 above the quarters destined for plants. Of these quarters 

 one was set apart for aquatics. In this division were laid 

 down six parallel compartments of troughs so united together 

 as to present the form of so many Greek ns, the heads of 

 these letters lying alternately in opposite directions (Fig. 1. C). 

 The troughs are one foot six inches in the clear, and of the 

 same depth (Fig. 2. C), they are made of oak planks three 

 inches thick, and well tarred. They are not laid upon 

 the bare ground, but on strong supporters (Fig. 2. B), 

 which arc also tarred, and fastened to stout posts (Fig. 2. A). 

 Stone pillars might also be used for this sub-structure. The 

 space below the cross pieces was kept clear the whole length, 

 so as to prevent the bottom of the trough from touching any 

 thing but its supporters. The troughs themselves received 

 a very slight inclination, not amounting to more than an 

 inch and a half in one hundred feet. This inclination gives 

 to the water a fall which is adapted to all plants ; it is suffi- 

 cient for those that admit of a stronger current, and not too 

 much for such as would be carried away by a quicker stream. 

 It is not easy to confine Salvinia natans within one division, 

 it will perhaps stray into the two adjoining ones, for where 

 it grows naturally, and is exposed to a more rapid current 



