14 University of California Publications in Botany [^ol. 7 



segments under 5 mni. in tliickness Avill produce shoots and increase 

 in size normally from year to year. We attempted to graft all 

 sizes of rootstock segments of sessile onto one another and to unite 

 portions of rootstocks of this species and of ovatum. A possible 

 increase in vegetative vigor of the grafted rootstock was anticipated. 

 It was also hoped that, in the case of interspecific graft unions, an 

 offset might be produced at the point of contact. A few successful 

 unions were obtained in both cases, but no visible effects could be 

 noted during the first year in the case of the shoots which were 

 normally produced from the crowns of the treated rootstocks. No 

 offsets were formed during this first year, and the experiments were 

 terminated because it was not possible to give the grafted rootstocks 

 sufficient care to prevent the drying out of the graft unions during 

 the dry season. 



Seeds of T. sessile var. giganteum have from time to time been 

 obtained, both of the white-flowered form of the northern counties 

 and also from plants in tlie Berkeley hills. Up to this past year it 

 has not been possible to secure germination of any of this seed, 

 although in all cases it appeared to be entirely normally matured. 

 The seed coverings were broken and softened by mechanical means 

 and by the use of sulphuric acid and were subjected to a variety 

 of growing conditions without securing a single germination. 

 Recently seeds from plants growing in the Berkeley hills have germ- 

 inated over 60 per cent. Apparently seed of the western sessile will 

 not germinate for eighteen months or longer if placed in the ground 

 as soon as mature, but if allowed a period of six to twelve months 

 or more for after-ripening will then germinate almost at once Avhen 

 placed under ordinary germinating conditions. The failure of our 

 earlier attempts at germination of this seed was due to a termination 

 of the experiment long before germination could have taken place. 

 Further experiments are in progress to confirm and amplify these 

 preliminary observations. Various stages of development in seed- 

 lings of tlie first year are shown in plate 4. The third and fifth 

 seedling from the left show the seed coats still attached. 



Nothing has been more striking throughout our field and garden 

 observations than the extreme development of vegetative propagation 

 in T. sessile var. giganteum, a condition which appears to be 

 accompanied by or a result of a highly defective power of sexual 

 reproduction. T. ovatum, on the other hand, very rarely forms a new 



