206 MORPHOLOGY OF ANGIOSPERMS 



Among the Monocotyledons such undifferentiated embryos ap- 

 pear among Orchidaceae and Burmanniaeeae, in the former 

 family the primary root never appearing; but they are even 

 more numerous among Dicotyledons. Goebel 28 states that the 

 embryo of Monotropa consists of five to nine cells, and that of 

 Pyrola secunda, quoting from Hofmeister, of eight to sixteen 

 cells. The entirely undifferentiated embryo of Aphyllon uni- 

 florum has been noted by Miss Smith 7S ; and the embryos of 

 Orobanchaceae (Koch 14 ), and of Balanophoraceae and Cytina- 

 ceae (Solms-Laubach 8 ), consist of a very small mass of tissue. 

 In this connection it should be noted, however, that in Cuscuta 

 and Viscum the embryos are large and "well developed. In 

 some non-parasitic forms also poorly developed embryos occur, 

 as in Utricularia (Kamienski 1J ), in which the embryo develops 

 no root-tip but produces a large number of peculiar leaves. 



The appearance of a single cotyledon in the embryos of 

 certain Dicotyledons has naturally attracted attention. As a 

 prefatory illustration, it may be observed that in Trapa natans, 

 one cotyledon is much smaller than the other, and this suggests 

 the possibility of further abortion and even of suppression of 

 one of the cotyledons. In Ranunculus Ficaria Irmisch 1 long 

 ago reported the occurrence of a single cotyledon sheathing 

 below, and Erianlhis hiemalis, Gorydalis cava, and Varum 

 (Buniiun) bulbocastanum have also been included in the list 

 of " pseudo-monocotyledons.'' In the case of C. bulbocastanum 

 Hegelmaier 10 discovered that the apparently single and ter- 

 minal cotyledon is accompanied by a second almost completely 

 aborted and lateral cotyledon. All of these forms have been 

 investigated recentlv by Schmid, 91 who discovered that in Eri- 



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anthis hiemalis the two cotyledons are of unequal size; that in 

 Ranunculus Ficaria there is hardly a trace of a second cotyle- 

 don, and that this trace was probably mistaken by Irmisch 1 

 for a sheathing base; and that in Corydalis cava there is only a 

 slight protuberance to represent the second cotyledon, the func- 

 tioning one in its growth gradually assuming a more terminal 

 position and thrusting the stem-tip to an apparently lateral posi- 

 tion, but in C. nobilis and C. lutea the normal development of 

 cotyledons is found. In Cyclamen persicum, also. Schmid 

 found embrvos in ripe seeds with no trace of a second cotvle- 



%J IT i 



don. From these cases it is evident that in certain dicotyled- 



