BOTANICAL SUBJECTS. 81 



in the same position that all the segments are, in the twisted 

 corolla of the Apocinacege — it is imbricate. 



There are other puzzles connected with the Gladiolus which 

 await solution, viz., {a.) Why are the lower segments the marked 

 ones, when, in the Iris and peloric Gladioli, the three segments of 

 the same whorl are marked ? (6.) What causes the exposed 

 labellum or labella in the irregular Gladiolus to be more brilliantly 

 coloured than the remaining two or one lower segments, as the 

 case may be ? (c.) Why are the three lower segments of the 

 Gladiolus so often smaller than the three upper ones ? 



One might be tempted to reply to the latter question (c) by 

 saying that this feature was inherited from some form like that of 

 G. Namaquensis, G. Viperatus, and others. But this explanation 

 only calls forth another question — Why have these that feature ? 

 Therein lies puzzle (c) . 



The lower petals are the landing place of insects that \^sit this 

 flower for its nectar, and, according to Prof. Henslow's theory (if 

 I read it rightly), the constant pressure of an insect will cause the 

 part pressed to enlarge.* Just the reverse appears to be the case 

 in these forms of Gladiolus ! What other sufficient reason can be 

 adduced for the reduction instead of the increase in size of these 

 lower petals which form the landing place of insects ? Were 

 they large or small insects that produced this feature, or was 

 the dwarfing totally unconnected with insect action ? 



A few diagrams will explain the matter I have been en- 

 deavouring to prove more readily than a whole chapter of words. 



Form of Gladiolus ^vith one labellum. Form of Gladiolus with two labella. 



* Are not insects a part of the surroundings? If so. Prof. Henslow's 

 theory admits that surroundings do tend to modify organisms, or at all 

 events they tend to induce congenital modifications. 



A p. 1724. F 



