94 



ing or almost erect young" stem. The roots are all densely 

 covered with root-hairs and unbranched. The leaves are 

 now considerably larger than in the state last described, but 

 the blade has not yet, however, assumed the normal shape, 

 which has been figured on Plate XIX, Fig. 164. The plant 

 continues its growth, as indicated (Fig, 162), and the whole 

 stem is entirely above ground without any proper rhizome. 



ALISMACE.E, 



CONCLUDING REMARKS. 



It is merely a matter of incident that has caused just the 

 above-mentioned species to have been described from their 



* Brisseau-MirbeL El^mens de Physiologie v6gctale et de Botanique, 

 1815, PI. 61. 





^ 



Alisma Plantago, var. Americana. \ 



The germination of the seed of this variety is the same as 

 that of the typical form, which has been so exactly figured 

 by Mirbel.^' 



The cotyledon is a relatively long, terete leaf, which 

 carries the testa of the seed at its summit for some time, and is 

 entirely above ground. A germinating plantlet is shown on | 



Plate XIX, Fig. 166, where the plumule (P) has not yet come j 



out, but is still to be found inside the base of the long coty- ^ . 

 ledon, that shows an incipient swelling at the place where 

 the plumule has to penetrate. There is between the base of 

 the cotyledon and the primary root a cylindrical body (C), 

 which is the hypocotyl, and we further see a distinct roll at 

 the transition from the stem to the root, which is densely 

 covered with hairs, and which Mirbel has explained as a 

 rudimentary coleorhiza. The primary root (R) is very short 

 and is not further developed, and is replaced by secondary 

 roots, of which the first one will come out at the base of the 

 cotyledon, just below the plumule, while the other parts of 

 the seedling, the hypocotyl, the rudimentary coleorhiza and 

 the primary root disappear very early. 



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