58 I'ROCKKDIXGS OK Till: 



Ameiitiferae. ProF. Jt-HVey (28. p. 1384) makes iiur-Ii capital of 

 this in opposing tiie llatiaiiaii standpoint. Tliu two characters ot 

 the wood cliieHy concerned bear on the nature ot" the ])erforatioii.s 

 of the vessels and on the composition ol' tlie medullary rays, lie 

 is carel'ul to dwell on the tacL that sc-alarifonu |)erlorations 

 characterise the wood of CusHctrina and the i'agales ; but refrains 

 fnnn laying stress also on tlu-ir abundance 111 the arborescL-nt 

 Kanales ! iiailey and 8iniiott (7) have advanced serious objections 

 to Jeffrey's aggregate ray theory, upon which the supposed 

 primitiveness of the medullary ray in tlie Aujcntit'erie rests. 



The view that of all Dicotyledons certain of tin; Ameiiti ferae 

 liave the least evolved type of wood is weakened by the fact that 

 some of the llunales, viz., Drimys, Zijr/oijifuiuu, Trochodendron, and 

 Tetracentron, are lacking in true vessels. Jeffrey dismisses the 

 matter in rather an arbitrary fashion by imagining that the vessels 

 have disappeared (28). These forms are woody plants, and if 

 vessels had once been present one wonders what can have led to 

 their sup|)ression. 



Monocoti/ledons. It is now tlieprevailing opinion that Monocoty- 

 ledons have descended from Dicoiyledons, that is to say that llieir 

 ancestors had two cotyledons. Except the cotyledonary distinction 

 there is no fundamental feature of difference between the two 

 groups. Some years ago the absence of cambium in Mouocoty- 

 ledons might have been held as fundamental, but in the light of 

 recent work (2) this deficiency has no or slight pliyletic value. 

 The geophytic or aquatic origin of Monocotyledons explains the 

 loss of tliis cambium, and the arborescent types, such as palms, 

 can he regarded in the light of new evolutions, in which the tree- 

 iiabit has been regained by the adoption of fresh means of 

 attaining stem-rigidity. This habit, broadly vie\\ed, is primitive 

 to the herbaceous in Dicotyledons, but the reverse may be con- 

 sidered to liold in tlie case of the Monoc-otyledons. 



It must be conceded on geological evidence that the Monocoty- 

 ledons are an old assemblage of flowering plants, and they must 

 ])tn"force have left the Dicotyledonous line of descent at an early 

 period. The question naturally arises, are they mono- or polyphy- 

 letic respecting their dfrivation froni Dicotyledons? Though no 

 satisfying answer can yet be given to this question, the writer 

 sees no cogent reason for regarding the group as other than niono- 

 phyletic and of possible Kanalian extraction. The tloral features 

 lu common between the lltdobieje on the one hand and the 

 Kanales (especially certain of the Nymphaeacete) on the other 

 hanil sug'^est something dee|)er than mere [)arallelism. The sup- 

 posed connection between the Piperacea^" and the Araceio, based 

 oriiritially by Campbell on gan.etophytic resemblances and later by 

 A. W . llili on the presence of hetcrocotyly in Pepcrooua, does not 

 appeal to the writer, because in both cases it is forcing an allinity 

 between highly evolved ratlier than between primitive members of 

 these families. 



