1590 



A TEXTBOOK OF THEORETICAL BOTANY 



was that a single cotyledon had been modified into a haustorium and was 

 therefore the only one of importance in the embryo. The appearance of 

 the second cotyledon was post-embryonic, and it was, in fact, the organ 

 usually called the first leaf. This is as much as to to say that Monocotyle- 

 dons are not monocotyledonous but only extremely heterocotylous. Lotsy 

 believed this to be true of the Araceae and he therefore accepted their 

 relationship to Peperomia, but it is much more difiicult to apply the argu- 

 ment to the Helobiae, which are more understandable on Miss Sargent's 

 view, and he accepted their derivation from Ranales. 



The striking fact is that in the Ranales there are a number of genera 

 which have monocotyledonous or pseudo-monocotyledonous seedlings, and 

 others which display further monocotyledonous characters, such as closed 



vascular bundles, scattered bundles in 

 the stem and absence of secondary 

 thickening, as well as trimerous flowers, 

 failure of the primary root, sheathing 

 petioles, a geophilous habit and the 

 absence of vessels in the secondary 

 w^ood (which is also true of those 

 Monocotyledons which are thickened 

 by means of a secondary cambium). 



The pseudo-monocotyledonous 

 seedlings form an interesting group, 

 with examples both in Ranunculaceae 

 and Berberidaceae, e.g., Ficaria verna, 

 Ranunculus iUyriciis and Podophyllum 

 emodi, though we are obliged to add 

 that isolated cases occur in other fami- 

 lies, e.g., Papaveraceae, Celastraceae 

 and Umbelliferae, where they can 

 have no phylogenetic connection with 

 Monocotyledons. Podophyllum emodi 

 aflFords a good type of the others 

 mentioned (Fig. 1450). The two coty- 

 ledons are united on one petiole, with 

 a sheathing base. There is no hypo- 

 cotyl and the plumule emerges from a 

 slit at one side of the base of the coty- 

 ledonary stalk and stands opposite to 

 the combined "cotyledon", as in Mono- 

 cotyledons. In some other species 

 {Delphinium nudicaule and Chelidonium majus) the union of cotyledons is 

 practically complete and in Biinium bulbocastanum and Corydalis solida there 

 is definitely only a single cotyledon. There is, however, a double vascular 

 supply in the petiole and by analogy with this. Miss Sargent relied on the 

 presence of a double vascular bundle in the cotyledon of Monocotyledons 



V\G. 1430. — Podophyl/iini riiiodi. Pseudo- 

 monocotyledonous germination. See 

 in text. (From Lubbock, "A Contribu- 

 tion to our Knozcledge of Seedlings".) 



