98 Macfarlanc — Obsen>atiofis on Some Hybrids 



these have been shown to be reproduced not in blended fash- 

 ion, but as distinct structures reduced either in size or number 

 or both. The elongated glandular hairs on the sepals of 

 D. filiformis, and the sessile two-celled glands of D. intermedia 

 ahke appear in the hybrid. Such a morphological pattern is 

 frequent in hybrids whose parents are somewhat removed in 

 systematic affinity, and suggests interesting cytological specu- 

 lation. For, if every cell in the hybrid be, as its structure 

 proclaims it to be, a combined effect of two parental condi- 

 tions each reduced by half, some appropriate explanation must 

 be given to the special case before us. As yet we have no 

 evidence which would militate against the view, and every- 

 thing is in favor of it, that every average cell of a hybrid has 

 an equal number of chromosomes and half as much chromatic 

 substance as is found in each parent. But for the production 

 of two such epidermal appendages some special line of devel- 

 opment must have been taken by the epidermal cell which 

 gave rise to each. The view would be an imperfect one 

 which would cause us to suppose that chromosomes repre- 

 sentative of one parent were alone present in such epidermal 

 cells. It will be more consonant with the principles of 

 heredity, if we suppose that at a certain cell centre in the epi- 

 dermis, a special growth-potentiality is inherited from one 

 parent, that stimulates to the formation of a hair characteristic 

 of it, and that while the hereditary influence of the other 

 parent, that is devoid of such hairs, is sufficient to reduce or 

 check back growth of the hair to at least half the size of the 

 parental one, it fails to prevent the development of a structure 

 peculiar to one parent alone. Neither is there any need to 

 suppose that there is a separation or sorting out of chromatic 

 elements in the process. Side by side on the same spirem 

 thread of the epidermal cell which produces such a hair, 

 elements of both parents may exist, and similarly also in each 

 cell that contributes to the hair formation. But the decidedly 

 reduced size, in the hybrid, of the glandular hairs inherited 



