424 MORPHOLOGY OF THE ANGIOSPERMS 



The secondary phloem of the Ranales is little known; only that of 

 the Calycanthaceae and Austrobaileyaceae (Fig. 26) has been critically 

 studied. In several families, it has been loosely described as "soft," 

 "nonfibrous," or "unstratified." Histological simplicity characterizes the 

 secondary phloem in most families, but perhaps only in the Calycantha- 

 ceae, Eupomatiaceae, Austrobaileyaceae, and Lardizabalaceae is this 

 tissue without sclerenchyma. Most of the families have "scattered 

 fibers," or "patches of sclerenchyma." Only the Himantandraceae and 

 Tetracentraceae are described as having "stratified phloem," as have 

 most woody higher orders. The Ranales seem to show all stages in the 

 specialization of secondary phloem as a complex tissue. 



Detailed histological structure of the secondary phloem of the Ranales 

 is not well known. In some families, the sieve-tube elements are of the 

 more primitive, elongate, tapering type. The Calycanthaceae have sieve 

 cells of high type — short, with transverse end wall; in this character, 

 they accompany in the family the high types of vessel element and seed 

 structure. This is a surprising group of advanced characters for a 

 ranalian family with primitive perianth, stamens, and pollination. The 

 phloem of Atistrobaileija (Fig. 26) is remarkable in its lack of com- 

 panion cells, a gymnosperm character, probably unknown elsewhere in 

 angiosperms. 



The Flower. Ranalian flowers, in addition to the generally recognized 

 polymery and absence of fusion, show much of the probable nature 

 and structure of the early angiosperm flower. The perianth is shown to 

 have arisen independently in different phyletic lines and, morpho- 

 logically, in different ways. In the Trochodendraceae, the flowers lack 

 a perianth, and there is no evidence of lost organs. Where a perianth is 

 present, the modified appendages surrounding the sporophylls are of 

 two basic types, vegetative and reproductive. Vegetative types are rep- 

 resented by decickious, calyptralike bud scales — one in Eitpomutia 

 (Figs. 143 and 144) and Himantandra — and by bracts, which range in 

 form from minute scales to leaflike, from deciduous to persistent, from 

 spiral — often connecting the phyllotaxy of the leaves with that of the 

 androecium — to whorled. Leaflike tepals are prominent in some families; 

 petaloid in others. Liriodendron and the more advanced species of 

 Magnolia and Asimina show stages in the differentiation of a corolla in 

 the form of whorls of three "petals" from the uppermost spirally borne 

 tepals. The flowers of Trochodendron are described as without peri- 

 anth, but possess scalelike organs below the flowers. Some flowers 

 without a perianth, except in the form of protective bud scales, are 

 probably primitively so — Eiipomatia (frontispiece and Fig. 143), 

 Trochodendron; others without a perianth — Cercidiphyllum (Fig. 146), 

 Euptelea — have perhaps lost their perianth. 



