Monotropaceae with Reference to Ericaceae 103 



In Ericaceae, the fruit is a capsule, with septicidal or loculicidal 

 dehiscence, or a berry. In the Pyrolaceae and Monotropaceae 

 the fruit is a capsule, as in the primitive Ericaceae. It is char- 

 acteristic of many Ericaceae, e.g., Cassiope hypnoides, C.tetragona, 

 Phyllodoce coerulea, that after flowering (in species with droop- 

 ing flowers) the pedicels straighten out so that the fruit becomes 

 erect. This is characteristic of all of the Pyrolaceae and Mono- 

 tropaceae. 



In typical Ericaceae, the seeds are small, the largest 1-2 mm. 

 The endosperm is well developed, the embryo distinctly formed, 

 a root and two cotyledons always present. In the Pyrolaceae 

 and Monotropaceae the seeds are smaller and more numerous. 

 In structure they are much reduced. The endosperm in the 

 Pyrolaceae consists of relatively few large cells — the embryo 

 of about 25-30 cells with no trace of cotyledons. In the Mono- 

 tropaceae the number of endosperm cells is still less and the 

 cells are larger, the embryo also is very small, composed of only 

 nine or five cells (43, 74). 



Summary 



In the Ericaceae the plants are shrubby or sub-shrubby. 

 The Pyrolaceae show a gradual reduction from sub-shrubby in 

 Chimaphila to herbaceous in Moneses. The Monotropaceae are 

 entirely herbaceous. The underground rhizome, producing ad- 

 ventitious buds and roots, in many of the Ericaceae, in Chima- 

 phila and Pyrola, gradually has its function of producing buds 

 and roots taken over by the root which becomes long and hori- 

 zontal in Moneses, becoming condensed to short and fleshy in 

 the Monotropaceae. There is a gradual increase in the amount 

 of hyphal investment in the roots from Chimaphila through 

 Pyrola to Monotropa, the most saprophytic, correlated with a 

 gradual decrease in the number of layers in the root cap. In 

 the structure of the ascending axis, there is a gradual decrease 

 in the amount of wood formed, from typical Ericaceae, with 

 very woody stems through Chimaphila which is as woody as 

 some of the smaller Ericaceae, through Pyrola and Moneses 

 which are less woody, to the Monotropaceae, reaching its climax 

 in Monotropa where the amount of wood is very limited. Cor- 

 related with this is a gradual increase in the amount of phloem. 

 There is a gradual reduction in the size and structure of the 



