CERTAIN CHARACTEBS OF HYBRIDS. 575 



with striking rapidity and exuberance; they not uncommonly flower the very first 

 year after they are sown, whereas the seedlings of the parent-species may not attain 

 to the flowering stage for two or three years; and in respect of the size of the 

 foliage, and still more that of the flowers, hybrids often exceed both parent-species. 

 The latter circumstance is indeed one of the chief reasons why growers make such 

 frequent use of the process of crossing. They are thus enabled to meet the demands 

 of connoisseurs, who prefer to have plants with conspicuous flowers in their gardens. 

 The augmentation in the size of the flowers usually ceases after the first, or at any 

 rate after the second year. Subsequently, the flowers of hybrids become smaller 

 again. On this account gardeners are in the habit of producing such hybrids as are 

 especially valued for their large flowers over and over again by the original method. 

 Of the large number of observations recorded on this subject we will here mention 

 one as an example. Isoloma Decaisneanwm of the order Gesneraceas is the product 

 of a cross between Isoloma Tydoewm and IsoloTna sciadocalyx. The seeds obtained 

 after crossing germinate early, and the seedlings develop rapidly into exceptionally 

 robust plants. The foliage-leaves are three times as large and the flowers twice as 

 large as those of the parent-species; in addition, the flowers are much more numerous 

 than on the parent-plants, and in consequence the hybrid has a much more imposing 

 and showy appearance than either of its progenitors. 



Many plants which grow on soil rich in humus in mountainous regions, such as 

 the Lungworts (Pulinonaria) and Primulas (Prvmula), do not thrive particularly 

 well in gardens, and certain species die after a short time even when cultivated 

 with, the greatest care. Yet the hybrids of such species flourish wonderfully well 

 under similar circumstances. They blossom luxuriantly, and may be kept in a 

 state of vigorous growth for many years. Examples of this are afforded by 

 Prvmula pubescens and Primula Venzoi. One of the parent-stocks of P. 

 pubescens, viz. Primula hirsuta, can only be reared if the soil used is expressly 

 prepared for itself, and if several other special precautions are taken, whereas the 

 hybrid, P. pubescens, grows exuberantly in ordinary garden-soil. The case of P. 

 Venzoi, the hybrid-offspring of Primula tyrolensis and Primula Wulfeniana, is 

 still more remarkable. Although both the parent species are reared with difficulty, 

 even when the greatest care is bestowed upon their cultivation, Primula Venzoi 

 will flourish with extreme luxuriance if planted close to them in the same soil and 

 under the same external conditions. 



Another phenomenon sometimes exhibited by hybrids is a change in the dis- 

 tribution of the sexes. It often happens, for instance, that hybrids produce 

 pseudo-hermaphrodite female flowers and pseudo-hermaphrodite male flowers (of. 

 p. 294), even where both parent-species have true hermaphrodite flowers. In 

 Willow hybrids a partial transformation of male into female flowers, and vice 

 versd, has been not infrequently observed, and we then have moncEcious catkins 

 bearing flowers, half of which are female and half male. This change also occurs 

 in true species, but only as a rare exception, whilst in the case of hybrids it is by 

 no means uncommon. 



