9^ I. H. Burkill — Flower of Ranunculus arvensis. [No. 2 



The symmetry of tlie flower depends firstly on this regular sequence 

 and separation of the moods; it depends secondly on the way in 

 which successive rings of organs,— sepals, petals, etc.— are commonly 

 isomerous. 



I have been driven to a conviction that the separation of these 

 moods has not yet obtained tlie attention it deserves. We need to 

 know much about them ; chiefly as to the conditions which lead to their 

 separation : for the whole Phanerogamic subkingdom shows us that 

 the rnore specialised a flower is the more distinctly nre its moods separ- 

 ated; and the isolation of the moods is undeniably of far-reaching 

 importance in the growth of perfect floral symmetry. 



It may be said that there are questions of four kinds to be asked 

 regarding the moods, (i) why the moods exist, (ii) as to the reason of 

 their sequence, (iii) as to the requirements which have made them as 

 distinct as they are, and (iv) as to the causes leading to a determination 

 of the number of lateral organs which belong to each of them severally. 



They are questions in organography, as Goebel terms the causative 

 morphology of the new school, in order to distinguish it from the 

 descriptive morphology which is subservient to the systematist. The 

 foundation of organography is in the Darwinian theory of evolution. 



The present paper concerns questions of the fourth kind ; but in 

 preface I wish to make some brief remarks regarding the second and 

 the third kind of question. Regarding the second : the sepals are 

 formed outermost to protect ; the petals are formed second to attract ; 

 and we have these reasons for the position of both ; but why the 

 mood for the formation of stamens should invariably precede that for 

 the formation of carpels is a question which must remain a subject for 

 speculation almost as long as the origin of the Phanerogams is unsolved. 

 This only can be said, that somehow the formation of female organs 

 puts a period to the forward growth of the axis, whereas the forming 

 stamens have divided with the axis the available nutrition passing beyond 

 the growing sepals and petals. This perhaps means some advantage in 

 the matter of food to one or the other. I do not say which : but it is to 

 be confessed that there are strong reasons for assuming that, in nature 

 generally, conditions of good nourishment tend more to the formation 

 of female than of male organs : for experiments on the lower plants — 

 Algae, Fungi and Vascular Cryptogams — have shown that there is a 

 tendency for female reproductive organs to be formed when the plants 

 are well nourished, male organs when they are starved : and extensive 

 observations on animals indicate the same thing. A condition so widely 

 true may well be true also of the Phanerogams; but at the present 

 time can we produce any convincing evidence that the developing bud 



