EFFECTS UPON GERMINATION 795 



pleto in darkness. These seeds germinated in dry air when removed from 

 the fruit and also in the presence of Uquid water if protected from bacteria 

 and fungi. 



Heinricher (38) found that Arceuthohium oxycedri, another epiphytic 

 and parasitic Loranthacean, required Hght for germination. Unlike 

 other parasitic Loranthaceae it would not germinate on glass or other 

 inorganic substrata but required a cellulose substratum for germination. 

 Pure Swedish filter paper proved excellent, and spruce wood was good. 

 Heinricher considered this as evidence that Arceuthohium was more 

 strictly parasitic than Viscum and Loranthus. Arceuthohium oxycedri 

 seeds could remain longer in darkness without losing their germinating 

 power than Viscum alhum seeds. After 3 months in darkness the seeds 

 still gave 7 per cent germination in light. 



Cannon (10) studied Phoradendron villosum and P. californicum, and 

 Peirce (82) investigated Arceuthohium occidentale, but since they were 

 unable to germinate the seeds, we have no information on the effect of 

 light on the germination of American parasitic Loranthaceae. Van 

 Tieghem (94) found that the seeds of Nuytsia florihunda, a species of 

 Loranthaceae which is not an epiphyte but a root parasite, retained their 

 vitality during 2 years of dry storage, and that they would germinate 

 in both light and darkness. 



Bessey (6) showed that seeds of the strangling fig, Ficus aurea, germi- 

 nated only in light, but the seeds of Ficus populnea, a less strict epiphyte, 

 would germinate in darkness but were favored by light. Seeds of Ficus 

 carica (51, page 16) and Ficus elastica (90) are also light-favored. 



Heinricher (34), who investigated several Bromeliaceae, found light 

 necessary for the germination of seeds of Pitcairnia maidifolia, mainly 

 a rock or soil inhabitant. He believed light a requirement for the 

 germination of seeds of most Tillandsieae, many of which are epiphytic. 

 Other groups of the Bromeliaceae showed different behavior. Germina- 

 tion of seeds of Dyckia rari flora and D. sulphurea was hastened only 

 slightly by light, and Aechmea coerulescens germinated equally well 

 in light and darkness. 



While most of the epiphytic parasites or epiphytes mentioned above 

 are favored in their germination by light, and some apparently require 

 light, there is no strict relationship between epiphytism and light require- 

 ment. Also no strict uniformity of behavior exists within the same 

 family of plants or even within the smaller more closely related systematic 

 groups, although certain systematic groups seem to have a large propor- 

 tion of species, the seeds of which are favored by light. 



A defect in all of the researches reported in this section is the failure 

 to study the favoring action of light under a sufficient range of other 

 conditions. This fact will become evident when the researches on Chloris 

 and Poa are discussed. 



