434 GROWTH OF PLANTS 



in the roots. Cuttings taken in August or September and including current 

 and previous year wood rooted readily; those taken in the spring root less 

 readily. Live sphagnum, native soil, peat moss, and mixtures of peat moss 

 and good sand were all good rooting media. 



There was found to be a great difference in the percentage of germination 

 in seeds taken from different fruits, the germination ranging from 0.3 to 

 87.3 per cent. Best germination occurred when the seeds were planted soon 

 after harvest. In open air storage the vitality of the seeds fell rapidly. 

 Batches of seeds that gave 45 per cent germination in July gave only 2 per 

 cent in the 5 out of 80 lots which showed any germination after storage 

 for six and one-half months. Arbutus is dimorphous as to style and stamens 

 and subdioecious and hand pollination mcreased the average set of seeds 

 per fruit from 241 to 403. Plants of trailing arbutus thrive over a wide range 

 of pH; plants did well in soils with pH anywhere between 4.65 and 7.67. 

 No observations were made in lower or higher acidity ranges. 



A later study ^ emphasized again the significance of the endophytic fun- 

 gus in the life of trailing arbutus. This fungus appears in the roots, stems, 

 leaves, and fruit and on the pollen, seed, and ovule. If the fungus is not 

 present, the gro's^ii.h of the plant is improved by the addition of soil from 

 around vigorously growing plants. Seedlings develop normally if fungus 

 is present. The root tip of this plant furnishes excellent material for study- 

 ing living chromosomes. 



The increasing use of several species of Lycopodiums (mainly collected 

 in the \vild) for Christmas decorations threatens the depletion of these 

 plants. Barrows ^' ^' ^ made a study of the propagation of several species 

 of the genus, hoping that commercial growing might protect the wald stands. 

 Her work with the germination of spores makes it quite evident that on 

 the basis of present knowledge the spores cannot be used as a commercial 

 means of propagation. After 30 months with the best cultural conditions 

 used, 15.8 per cent of the spores of L. complanatum var. flabelliforme ger- 

 minated. In 28 months L. ohscurum spores gave 20 per cent germination. 

 In no case did the gametophyte, prothallium, develop beyond the 10-cell 

 stage. The problem of securing more advanced development on artificial 

 media remains unsolved. The 10-cell stage is far short of a mature prothal- 

 lium with archegonia and antheridia, and finally with the sporophyte 

 resulting from the fertilization of the egg. While apparently some previous 

 investigators working with other species produced mature gametophytes 

 and sporophytes from spores, most workers have met difficulties similar to 

 or even greater than Barrows in spore germination and growth of the pro- 

 thallium. 



In fact, most of our knowledge of the gametophyte of Lycopodium species 

 has been gained from material collected in nature. The gametophytes 

 are not abundant in nature but they have been found repeatedly in various 

 stages of maturity. It is a challenge to the botanist to learn how to grow 

 a species of Lycopodium from spores with the same assurance he now grows 



