MINUTE STRUCTURE OF PLANT HYBRIDS. 283 



organism which neither parent possesses separately, we have good reason for the exercise 

 of caution before pronouncing decisively against species production from hybrids. Still 

 it must be confessed that our experimental statistics are so meagre and unsatisfactory that 

 no final opinion can be given. In saying this we do not in the least under-estimate the 

 conclusions arrived at by Kolreuter, Gartner, and their successors, but the wonderful 

 effects of altered conditions of soil, climate, and situation in giving relative fertility to 

 hybrids that were formerly regarded as sterile were not fully recognized in their day, and 

 are only now being to some degree appreciated. 



Strong reasons can be urged for the prosecution of careful and prolonged investiga- 

 tions on the subject in our botanic gardens, experimental stations, and private gardens. 



Though a partial investigation has already been made, no account has been taken in 

 this paper of second or third hybrids, or of hybrids in which, by reciprocal crossing, 

 different results are got. These will be treated of in a subsequent paper. 



The author gladly acknowledges the help received from various quarters since 

 commencement of this investigation. Valuable supplies of material have been received 

 through the kindness of the Directors and Curators of Kew, Glasnevin, Edinburgh 

 and Glasgow Botanic Gardens, and from many private sources. The constant aid 

 extended by Professor Balfour and Mr Lindsay deserve special mention, while Mr 

 Kichardson and Mr Forgan have given valuable help and advice on micro-photographic 

 details. Through the generosity of the Botanical Committee of the Eoyal Society, 

 a grant was given for purchase of material and illustration of the paper. 



October 1891. 



Explanation op Plates. 



VOL. XXXVII. PART I. (NO. 14). 2 S 



