364 University of California Publications in Agricultural Sciences [Vol. 



Variety Plant Xo. 



giganteum 13a 



sylvestre la 



lb 

 Ic 



In agreement with the results of Erith, I found no difference in 

 flower size in the two varieties. Apparentl}' the increase in size in 

 giganteum is only in the vegetative parts. In accordance with this 

 is the fact that the pollen is about the same size in the two varieties, 

 whereas the cells of the roots are considerably larger in giganteum. 

 The same was found to hold true for the stolons by Erith (1924, 

 pp. 110-111) who states, "In older plants the stolons of giganteum 

 have a diameter two to three times that of sylvestre, the larger 

 dimensions of the former being due to a greater number of indi- 

 vidually larger cells." 



The origin of giganteum is not known, but very likely it arose 

 from sylvestre. The genetic relations of the two varieties have not 

 been determined, but some study has been given to chromosome size 

 in Fi hybrids. Plant 1ft of sylvestre was crossed with plant 13ff of 

 giganteum. with la as the mother plant. The Fj plants are still too 

 young to make possible any conclusion as to the behavior of plant size 

 in this cross. Two somatic metaphases from Pj are pictured in 

 figure Se and /. The chromosome size is intermediate, being nearer 

 to that of the giganteum parent. This result suggests that the case 

 may be one of Mendelian inheritance of chromosome size. Mendelian 

 inheritance of a chromosomal character has been recorded by Lesley 

 and Frost (1927) in Matthiola, in which they found that one 

 Mendelian factor was responsible for the difference in shape of the 

 metaphase chromosomes of the first meiotic division. Because of lack 

 of material of the variety sylvestre, more work must be done to com- 

 plete the study of chromosome size in T. repens. As this species is 

 self-sterile, all the varieties are very heterozygous, and the plants 

 used by the writer were very variable in morphological characters. 

 One might expect, therefore, to find many chromosome sizes. It is 

 lioped that it will be possible to follow up this problem by further 

 study of the parent varieties, the Fj, and later generations. As the 

 cytological work of the writer has been discontinued, at least for some 

 time, it seems justifiable to give a preliminary account of it. 



