348 Transactions. 



a cambium is differentiated, still the amount of xylem formed remains 

 constantly very small, point to reduction. 



As a general rule, among herbaceous, bulbous, &c, Monocotyledons 

 the primary root disappears with the cotyledons. In M. excelsum there 

 is early loss of the primary root, and great development of adventitious 

 roots ; there are numerous adventitious roots from the nodes in P. End- 

 licheri. The loss of the primary root is, in all cases, probably connected 

 with geophilous characters. Among the Ranunculaceae, which are ad- 

 mitted to be primitive, Eranihus shows the primary root replaced in the 

 second spring by a circle of roots. 



Leaf. 



The leaf- venation seen in M. excelsum somewhat resembles that seen 

 in such Aroids as Zantedeschia, Arum. Professor Areschong has remarked 

 that the linear leaves characteristic of most bulbous Monocotyledons are 

 better adapted to push upwards through the soil than any dicotyledonous 

 type ; and that the bulbous plant seems in many respects the most highly 

 specialized form of geophyte, its squat axis and pointed leaves, with broad 

 sheathing base, being clearly adaptations to geophilous life. 



In M. excelsum the leaf is pointed, often sharply so, especially in very 

 young plants. There is always a sheath to the petiole, which entirely 

 covers the young bud or young leaf, and is clearly a protective organ. In 

 P. Endlicheri the leaves are more pointed in the young plant than in the 

 old ; but here the epidermis is of several layers., and stores water. 



Hypocotyl. 



Although details of transition in the hypocotyl are not rigid in the 

 Piperaceae, they may still be of value. A similar type of structure has 

 been found by different investigators in the Ranunculaceae, generally 

 acknowledged to be primitive ; in the Labiatae, Centrospermae ; in all 

 examined Papaveraceae, Capparidaceae, Resedaceae. Cruciferae ; in Pinus 

 maritima ; and in many Monocotyledons. The same may perhaps in time 

 be shown for further orders. Is it not possible, then, that the hypo- 

 cotyledonary structure may be of phylogenetic value in showing a line 

 of connection, or it may be common ancestry, for Monocotyledons and 

 Dicotyledons ? 



It would seem, then, that Macropiper is a primitive form ; Peperomia 

 an advance with reduction ; while Monocotyledons may have arisen as 

 modifications and reductions of the dicotyledouous type, as more specialized 

 forms, though earlier in time, perhaps, than the Piperaceae. The course 

 of advance is. however, still shown by the relation of Peperomia to Piper, 

 where the reductions arising in the former in response to environment are 

 all in the direction of Monocotyledons, the monocotyledon ous type most 

 closely resembled being the Araceae. 



In the specialization and reduction of Peperomia we see tendencies 

 which have become firmly established in Monocotvledons. 



