LIFE OF PLANTS. 



259 



part of the knot, and rises from thence into the plant. We 

 thus perceive, that in plants of the higher kinds, the cotyle- 

 dons are a necessary instrument of germination and growth ; 

 on which account, wlien both the cotyledons are cut off, the 

 plant of necessity dies. 



386. 



The distinction which has been made, chiefly since the 

 time of Ray, between the Acotyledonous, Monocotyledonous, 

 Dicotyledonous, and Polycotyledonous plants, — a distinction 

 which still prevails in the system of J ussieu, — entirely vanishes 

 upon a more exact and more general observation of nature. 



Among the Acotyledonous plants were mentioned the Fun- 

 gi, Algas, Lichens, Homallophyllae, Musci hepatici and fron- 

 dosi. Ferns, and Naiadae. But it has been already shewn 

 (30^, 307.), that Fungi, Algae, and Lichens, are propagated 

 by germs only ; and that Homallophyllae, Musci hepatici and 

 frondosi, and Ferns, during germination, produce fluctuating 

 forms, which might be regarded as representatives of the co- 

 tyledons. In the Naiadae, the thickened cotyledonous end of 

 the root renders, in most instances, the cotyledons superfluous, 

 and in some cases the albuminous substance, {Zoste?'a, Rup- 

 pia, Za7inichellia^ Potamogeton.) In other Naiadae i^Lemna, 

 Hippuris), the embryon is entirely unevolved in the middle 

 of the albuminous substance ; and in others {Callitriche, Ce- 

 ratcyphyllum^ Myriopliyllum)^ the embryon evidently divides 

 itself into two cotyledons. 



With respect to what are called Monocotyledonous plants, 

 Jussieu has reckoned them in this order, the Aroidae, Cype- 

 roidae. Grasses, Palmae, Restiaceae, Junceae, Sarmentacese, 

 Coronariae, Irideae, Hydrocharidae, Scitamineae, Musea^, Or- 

 chideae, and Pipereae. But in none of these plants can we 

 admit the existence of a proper cotyledon. Indeed, Mirbel 

 (Annal. du Mus.), Fischer (Ueber die Existenz der Mono- 

 und Polycotyledonen), Smith (Linn. Trans.), and Trevira- 

 nus (Entwickelung des Eyes), consider the vitellus in the 

 Scitamineae, or the bodies resembling scutella in the Grasses, 

 as cotyledons ; because there is a distinct transition from 



II 2 



