MINUTE STRUCTURE OF PLANT HYBRIDS. 255 



after to notice that while the young stems and leaves of the first had bleached completely, 

 those of the second had taken on a deep, dull, brown- grey colour, and those of the third a 

 tint inclining to the second, but greatly lighter. The colour suggested the probable presence 

 of tannin, and on application of the iron test this was verified. Sections of fresh leaves of 

 C. Laburnum gave a faint but undoubted tannin reaction, those of C. purpureus turned 

 to black-brown, while the hybrid assumed a hue considerably darker than in C. Laburnum. 

 That the hybrid inherits about half the amount of tannin supply, compared with the 

 sum-total of the parents, is evidenced if we take into consideration the large leaf surface 

 which it forms and through which the tannin has to be diffused. 



As yet only a few seminal hybrids have been noticed, which from their behaviour 

 suggest similar results. These are — (a) Geum intermedium and its parents ; G. rivale, 

 discolouring to a brown hue, and G. urbanum, to a white or whitish-yellow. (6) 

 Saxifraga Andrewsii and its parents, (c) Ribes Culverwellii and its parents ; but none 

 of these have been chemically tested. 



Odour of Hybrids and of their Parents. 



This resolves itself also into a chemical inquiry, but practically no attention has been 

 given to it hitherto. A few notes may be recorded. The common Sweet William 

 (Dianthus barbatus) is strongly and agreeably scented ; D. alpinus has no odour ; D. 

 Grievei has an odour like that of the first, but decidedly reduced in strength. 



Rhododendron Edgeworthii is an agreeably and powerfully scented species, with large 

 blooms ; R. ciliatum has small blooms, and is scentless or nearly so ; the hybrid has a 

 pleasant odour, that entirely agrees with the first physiologically. 



The large white blossoms of Hedychium coronarium give off a powerful and agreeable 

 odour, greatly reminding one of that from the butterfly orchid ; the smaller yellow 

 flowers of H. Gardnerianum give off a heavy odour, which in the opinion of most is 

 not particularly pleasant ; the hybrid gives off an odour which physiologically strikes 

 one as quite different from either parent, but unless by chemical analysis one could not 

 tell whether it results from commingling of the other two or is an entirely new chemical 

 combination. A wide series of observations on this subject is greatly to be desired. 



Flowering Period of Hybrids and of their Parents. 



It is a matter for regret that our information on phenological phenomena is extremely 

 meagre. Till within the last ten years the only continuous observations that have been 

 made and recorded, so far as I know, are those from the Edinburgh Botanic Garden ; but 

 they covered a very limited field, and have only been extended widely within the period 

 just named. Professor Hoffman's valuable tables and notes have not helped me, as 

 they refer to a limited number of true species only. 



The behaviour of some well-known hybrids and parents led me to watch the flowering 



