of Colour and Form in Plants* 405 



In conclusion — 



1 . The primaries, red, yellow, and blue, are generally present in 

 some part or other of the plant. 



2. When a primary occurs in any part of a plant, its comple- 

 ment will usually he found in some other part [or at some period or 

 other of the development of the plant, as was suggested to me by 

 Professor M^Cosh). 



Observations on the same subject in the animal kingdom have 

 occupied my attention during the past twelve months ; Birds, 

 Mollusca, and Radiata present associations of colour not less 

 remarkable than those here recorded. 



The relation between colour and form may now be examined, 

 and the remarks, for the present, have reference to the parts of 

 the flower. 



When the calyx and corolla are equal in size and similar in 

 form, the flower is regular ; differences in size and form are found 

 in irregular flowers. For example, the Violet has an irregular 

 flower, that of the Wallflower is regular ; a Primrose has a regular 

 flower, a Snapdragon presents an example of irregularity. Such 

 expressions are equally applicable to monocotyledonous and to 

 dicotyledonous plants, to polypetalous and gamopetalous corollae. 



Law 1. In regular polypetalous and gamopetalous corolla; the 

 colour is uniformly distributed, whatever be the number 

 of colours present. 



That is to say, the pieces of the corolla being all alike in size 

 and form, have each an equal proportion of colour. The com- 

 mon Primrose is an example where one colour only is present. 

 In the Chinese Primrose the same holds where two colours (one 

 the complement of the other) are present ; the eye or centre is 

 yellow, the margin purple. These two colours in this regular 

 flower are uniformly diffused, that is, each piece has an equal 

 proportion of yellow and of purple respectively. In Myosotis, 

 Anagallis, Erica, Pyrola, Gentiana, &c., we have instances. All 

 coroUifloral Exogens with regular flowers are examples ; the same 

 is true of certain Thalamiflorse, as Papaveracese, Cruciferse, &c. 

 In Jberis coccinea, belonging to Crucifera?, we find unequal size 

 of petals, but equal distribution of colour, because regularity of 

 flower is -the law in that family. 



Calycifloral Exogens with regular flowers are also examples, 

 as Rosacese, Cactacese, &c. 



Law 2. Irregularity of corolla is associated with irregular distri- 

 bution of colour, whether one or more colours are present. 



The odd lobe of the corolla is most varied in form, size, and 

 in colour. 



