270 PLANT HYBRIDIZATION BEFORE MENDEL 



Further details from Macfarlane's rather exhaustive anatom- 

 ical studies cannot be given, but the above will suffice to show 

 the manner of the investigations, and the general type of the 

 results. 



Some general conclusions which Macfarlane derives are inter- 

 esting. In e.g., the production of epidermal hairs, it is stated: 



"if the parents possess one or more kinds that are fundamentally simi- 

 lar, but which differ in size, number and position, the hybrid reproduces 

 them in an intermediate way. ... If the hairs of two parents are pretty 

 dissimilar, instead of a blending of these in one, the hybrid reproduces 

 each, though reduced in size and number by half." (p. 270 6e.) 



"The distribution of stomata over any epidermal area has been proved 

 to be a mean between the extremes of the parents, if the stomata of 

 the parents occur over one surface or both, and if the leaves are similar 

 in consistence, but ... if the stomatic distribution and leaf consistence 

 differ in the parents, this may give rise to correspondingly different re- 

 sults in the hybrid." {ib., p. 271.) 



". . . every hybrid has yielded a large series of examples which prove 

 the size, outline, amount of thickening, and localization and growth of 

 cell walls, is, as a rule, intermediate between those of the parents." 

 {ib., p. 271.) 



Interesting is the account of the laying down of secondary 

 cell-wall thickenings, which, whether of a cuticularized, lignified, 

 or colloid nature, in the hybrid constitute a mean in amount and 

 mode of deposition between the extremes of the two parents. The 

 most striking illustration is that of the bundle-sheath cells of 

 Philageria and its parents, where 5 lignified cell-lamellae are 

 found in Lapageria, 11-12 in Phtlesia, and 8-9 in Philageria. 



In leaves of the same age and like position, the chloroplasts, 

 in depth of color and size, are found to be intermediate in the 

 hybrid. (Saxzfraga, ib.^ p. 272.) 



As the result of his histological investigations, Macfarlane came 

 to the conclusion that the male and female elements in the fer- 

 tilization, act complementarily to a degree amounting to half, for 

 each of the two sexes, in the fertilization product. The principal 

 comment is as follows : 



"No matter what tissue or set of tissues is chosen, if the cells compos- 

 ing such are tolerably diverse in the parents, one can trace with ease the 

 modifying action which both sex elements have had on them, while these 

 clearly prove that each sex element, after union with its complementary 

 element, represents potentially half its former individuality, or retains 

 half its former hereditary properties." {ib., p. 273.) 



