44 Henderson — Comparative Study of Pyrolaceae and 



The writer, however, is concerned with saprophytism alone. 

 In the Burmanniaceae, for example, the genus Burmannia shows 

 transitions from green leafy plants with several racemose flowers 

 as B. longijolia Becc. to gradually condensing forms, as B. 

 azurea Griff, with a rosette of tiny herbaceous membranous 

 leaves and one to four flowers, then to more simplified forms, 

 as B. tuber osa and B. Candida, and finally, most simplified of all, 

 to the genera Thismia and Gymnosiphon. The stems become 

 feeble, less green, then reddish or brownish. The green leaves 

 become reduced to herbaceous membranous leaves, then to 

 scales; the flowers become reduced in number and size; the ovary 

 becomes reduced from a three-celled condition with central 

 placenta to a more primitive one-celled state with parietal 

 placentas (Gymnosiphon) ; there is an increase in the number of 

 ovules, but a reduction in their size; the seeds are reduced in 

 size and structure; the reserve albumen is reduced in size and 

 number of cells, and the embryo from a typical monocoty- 

 ledonous one to a formless mass. 



The writer would claim that essentially the same set of changes 

 can be traced in genera of the Orchidaceae and Gentianaceae. 

 Green autophytes, passing by gradual changes to colorless 

 saprophytes, occur in both of these. Now, among systematists 

 of the past, there has been no thought of putting the sapro- 

 phytic plants of the above three groups in separate families. 

 Why then, it may be asked, should the Pyrolaceae and Mono- 

 tropaceae be separated from the Ericaceae? It will be the 

 writer's aim in the present paper to prove, alike on morpho- 

 logical and physiological, as well as taxonomic grounds, that 

 these three families all show so close a relationship that to view 

 them as separate families is unnatural and artificial. 



Jussieu (37) considers all ericaceous plants under the two 

 orders — Rhododendra and Ericae — the latter including Pyrola. 

 Lindley (46) places them in three orders — Ericeae, Vaccinieae, 

 and Pyrolaceae (including Monotropaceae). De Candolle (10) 

 makes four orders — Vaccinieae, Ericaceae, Pyrolaceae, and 

 Monotropeae. Gray (25) considers the Vaccinieae, Ericineae, 

 Pyroleae, and Monotropeae as suborders of the Ericaceae. 

 Baillon (3) considers the Pyroleae, Monotropeae, and Ptero- 

 sporeae as three of the eighteen tribes under the Ericaceae. 

 Bentham and Hooker (4) make three orders, the Vacciniaceae, 



