THE PAST HISTORY OF MONOCOTVLEDOiNS 217 



regarded as the more primitive and dicotyledons as derived from 

 them. 



As an exponent of this view we may select the classification of 

 Engler with some modifications, and follow the generalisations of 

 Dr. Rendle,^ whose conclusions must largely be teased upon the vast 

 and unequalled collections of dried specimens in the National 

 Herbarium, supplemented by a knowledge of the living forms repre- 

 sented in the Royal Botanic Gardens at Kew. 



Dr. A. B Rendle ^ adopts Engler's view that Pandanales are the 

 most primitive. The flower of TypJia recalls the gymnospermic 

 strobiloid flowers. They are held to represent developments from a 

 common ancestor along different lines. 



Helobieas are next in order, and Naias is the most primitive, with 

 micro- and mega-sporangia, axial in origin. Glumiflorce have flowers 

 typically naked, and "correlated with this is the suggestion that the 

 group represents a primitive and not a reduced type of monocotyle- 

 dons, which have developed on their own lines." It is said to 

 "suggest a derivation from an earlier, more strictly aquatic group," 

 and " that it was the first group to become established upon the 

 drier land surface." 



In regard to Spadiciflorte, similarity of seed-structure serves to 

 unite palms and aroids here. Dr. Rendle thmks they may represent 

 a further development of Pandanales. 



Lemnaceae are a reduced type of Aroideae, wh')se huge herb type 

 is an adaptation to a hot, moist climate, and an outcome of this is 

 the epiphytic form, whose origin may be traced in Philodendron. 

 Assuming Glumiflorae to be primitive, the higher types follow on from 

 them. 



FarinoscC (including Restiacese, Eriocaulaceee, Commelinacege, 

 Pontederiacese, Bromeliaceae) are limited in range and highly 

 specialised. The Restiaceae suggest a glumiflorous type, adapted 

 to dry conditions which Glumiflorag in many points appear to confirm. 

 The Eriocaulaceae and other families are also highly specialised. 



The Liliiflorje include Juncaceae, which appear to be derived from 

 Glumiflorse. Liliaceje are closely related to them. Iridacea;, how- 

 ever, appear to exhibit reduction. In these and in the Liliaceje and 

 Ama'ryllidaceae there is a marked development of corms and bulbs, 

 and the plants are adapted to land areas not occupied by a meso- 

 phyte vegetation. 



In aloes and yuccas we find an increase in stem by secondary 

 growth to meet xerophytic conditions on a larger scale; the leaves 

 also are larger and more numerous. In Smilax both leaf and flower 

 structure are adaf)ted to a climbing habit. 



The Scitamineai are derived from some of the Liliifloriie. Musa is 

 the most primitive, and all are adapted in their herbaceous characters 

 to a moist climate. 



^ " The Classification of Flowering Plants, "' 1904, p. 378 et seqq. 

 - Ibid. 



