2o8 NATURAL SCIENCE. March, 



by a separate pollen-grain ; and but very few pollen-grains could be 

 found in the female figs. Although it is possible that in some cases 

 ordinary pollination may occur, the author asserts that the embryo is 

 usually formed without any process of fertilisation, arising as an out- 

 growth of the embryo-sac. The full development of both the male 

 and female flowers appears to depend on a simple hypertrophy of 

 the tissues of the fig, resulting from the irritation caused by the 

 female insect in the act of laying its eggs within the ovary of the 

 " gall-flowers " of the male figs, and of their persistent attempts to do 

 the same within the flowers of the female figs, in which attempts 

 they are frustrated by the great thickness of the wall of the ovary. 

 In connection with the fertilisation of the fig, it may be mentioned 

 that Professor Riley has enumerated fourteen species of insect as 

 taking part in the so-called " caprification " of the wild figs of North 

 America. He recommends to the fig-growers of California the intro- 

 duction for this purpose of Blastophaga psenes. 



With regard to the connection between the duration of life of the 

 individual and the mode of fertilisation, Meehan makes the general 

 statement that flowers which are wholly dependent on insects for 

 their fertilisation are always perennials, and that an innumerable 

 number of their flowers fall unfertilised ; while all annuals, on the 

 other hand, can self-pollinate themselves when cross-pollination fails ; 

 and in almost all cases all the flowers of annuals are fertile. 



The phenomena of hybridity in the vegetable closely resembles 

 those in the animal kingdom. It is possible to fertilise an ovule by 

 pollen belonging to a different species, but only if the two species are 

 very nearly allied. It is very rarely that species which are fertile 

 with one another can be placed in different genera. Hybridisation is 

 one of the every-day resources of the gardener ; but that cross- 

 breeding occurs in nature has been doubted by some. There seems, 

 however, scarcely to be room for doubt that in some of our abundant 

 wild genera, such as Rubus, Salix, and Hieracium, hybridity is not un- 

 common in nature. It has long been known that in some genera, such 

 as Passijlova, and in some Orchideae, the ovules appear to be even 

 more readily fertilised by pollen of a different species. W. Focke 

 now states that this is also the case with the species of Lilium belonging 

 io the grou^ bulb if evtim, and with some species of Hemerocallis; and 

 J. H. Wilson affirms the same respecting the Cape genus Albuca, also 

 belonging to the Liliaceae. According to Millardet none of the 

 so-called hybrid vines cultivated in Europe are true hybrids, i.e., 

 products of the crossing of distinct species ; they all spring from the 

 crossing of different races of the same species, Vitis vinifera. He 

 further states that, in the vine, it is the male parent that exercises the 

 preponderating influence on the descendants. Rimpau has carried 

 out a series of experiments on the crossing of some of our most 

 common agricultural plants. He has obtained ten artificial and nine 

 natural hybrids in wheat, and also obtained a fertile hybrid between 



