40 On Hybridisation of some Species of Salix 



the hybrid H^hHi leaves are hairy, though less densely so than in the 

 parent S. viminalis. 



(c) Stipules. 



Leaves of S. wultinervis are exstipulate (cf. Text-fig. 1 B, p. 37), 

 whereas those of S. gracilistyla are stipulate (cf. Text-fig. 1 A). The F^ 

 plants may be said to be a mosaic of the two parents respecting the 

 behaviour of stipules, for each individual is always provided with 

 both kinds of leaves, stipulate as well as exstipulate, and even in one 

 branch those with stipules may alternate with those without them. 

 The degree of their development is also very variable in different leaves, 

 because they are sometimes very conspicuous (cf Text-fig. 1 C, p. 37), 

 sometimes very insignificant being represented by mere tiny scales ; not 

 rarely we have one unpaired stipule on one side of the leaf In F^ 

 plants we see generally the same behaviour of stipules as in F^, for 

 then they are provided both with stipulate and exstipulate leaves. 

 Besides such plants we have some F^ individuals where we could yet 

 find no stipulate leaves, i.e. where all leaves are exstipulate exclusively ^ 

 Thus of 232 plants examined we have 170 with both kinds of leaves 

 and 62 with exstipulate leaves only. The latter plants are already six 

 to seven years old, and are pretty advanced in their growth, for many 

 of them are more than 1 metre, and some .even IJ metre high, and are 

 provided with a large number of branches. One might therefore be 

 led to conclude that they really lack stipules, and are the segregates 

 in a Mendelian sense, but I think that such a definite conclusion 

 may yet be considered as too hasty, because I have many times 

 experienced the fact that plants which were at first provided with 

 exstipulate leaves only, were later found to produce some leaves which 

 are clearly stipulate. Thus it is not unlikely that the 62 plants referred 

 to above, in which exstipulate leaves were exclusively found so far, 

 may in future bear some stipulate ones. And if the latter alternative 

 really holds good, then perhaps w^e have here a case of the so-called 

 " blending inheritance " or " constant intermediate inheritance " where 

 the behaviour of stipules in F^ , which is intermediate between that of 

 the two parents, always repeats itself throughout later generations. 

 But if, on the contrary, it be proved beyond all doubt that in F^ we 

 have a certain number of plants with exstipulate leaves exclusively, the 

 segregation of the characters " stipulate " and " exstipulate " may be 



^ All F2 plants were examined for stipules every year, and several times each year in 

 different stages of the development of their branches. 



