208 MORPHOLOGY OP ANGIOSPERJIS 



edge in Nuphar lutea. In his recent study of Ceratophyllum 

 Strasburger 8i finds that the embryo in its earlier stages bears 

 a striking resemblance to that of Nelumbo, there being a large 

 spherical mass of cells with no suspensor (Fig. 80). The em- 

 bryo of Nelunibo has the rudiment of a root, although it never 

 develops, the first functional roots corning from the stem above 

 the cotyledon (Fig. 80, s). In Ceratophyllum the reduction 

 due to the water habit has gone further, not even the rudiment 

 of a root appearing in the embryo. The two cotyledons of 

 Ceratophyllum so strongly resemble the condition. in Nelumbo, 

 that Strasburger, after examining the embryo of the latter, was 

 forced to believe that here also, as in Ceratophyllum, there are 

 two cotyledons. 



The occasional occurrence of a whorl of three cotyledons 

 has been reported for Quercus, Amygdalus, Phaseolus, etc., and 

 many other cases are given by Braun. 



In this connection, recent suggestions as to the pkvlogeny 

 of the cotyledon may be referred to. The current opinion re- 

 gards it as a modified foliage leaf, ami this is borne nut in the 

 majority of Dicotyledons by the assumption of the foliage func- 

 tion. The terminal cotyledon of Monocotyledons, however, 

 seems to belong to a different category, and to hold no relation 

 to a foliage leaf or to a foliar member of any description. In 

 a recent paper II. L. Lyon 8S develops the idea that the cotvle- 

 don of Angiosporms is phylogenetieally related to the sucking 

 organ known as the " foot " among Bryophytes and Pterido- 

 phytes. His own summary makes his position clear: 



(li The typical embryos of the Pteridophytes and Angiosperms 

 differentiate into three primary members, tbe cotyledon, stem, and 

 root; (2) cotyledons are not arrested leaves, but are primarily hausto- 

 rial organs originating phylogenetieally as the nursing-foot in the 

 Bryophytes and persisting throughout tbe higher plants ; (3) themono- 

 cotyledonous condition is the primitive one and prevails in the Bryo- 

 phytes, Pteridophytes, Monocotyledons, and some Gymnosperms ; the 

 two (sometimes more) cotyledons of the Dicotyledons are jointly the 

 homologue of the single cotyledon of the Monocotyledons; (4) the 

 cotyledon always occurs at the base of tbe primary stem ; (5) the hypo- 

 cotyl is a structure peculiar to the Angiosperms, being differentiated 

 between the primary stem and root; (6) the so-called cotyledon of 

 the Pteridophytes and Gymnosperms, with the probable exception cf 

 Ginkgo and the Cycads, are true foliage leaves. 



