Da. lo, 1 8 74] 



NA TURE 



II I 



comparison of Fig. 46 with 48 and of 49 with 50, the 

 anthers of the short-styled form .ire placed at the same 

 height in the corolla-tube as the stigma of the long-styled, 

 and, conversely, the stigma of the short-styled at the same 

 height as the anthers of the long-styled form. Hence the 

 same part of the body (head or proboscis) of any visiting 

 insect which has touched the anthers of the short-styled 

 form touches the stigma of the long-styled form, and con- 

 versely, so that by the regular visits of insects, flowers 

 of the long-styled form are fertilised by pollen of short- 

 styled flowers, and vice vcrsA. Thus in Primula officinalis 

 and villosa, as in all dimorphic species, intercrossing of 



different plants takes place naturally; and, as Mr. Darwin 

 has proved by experiment, is the only manner of fertilisa- 

 tion that is followed by perfect fertility. But whilst iden- 

 tical in the arrangement of all the parts of the flower and 

 in their remarkable sexual relations, our two species of 

 Primula differ in the wideness of their corolla-tube to such 

 an extent that the wide mouth of the flower of P. offici- 

 nalis is capable of including the whole head of a humble- 

 Ijee ; whereas the narrow corolla-tube of P. villosa is not 

 capable of including anything larger than the proboscis 

 of a humble-bee (compare the corolla-tube in Figs. 46 

 and 48, which, although three-and-a-half times magnified 



Fro SI. Fi( 



appears hardly as wide as the mouth of the flower in 

 Figs. 49 and 50, which is the natural size). In conse- 

 quence of this narrowness, the flowers of P. villosa are 

 not only unavoidably cross-fertilised when visited by but- 

 terflies, but they are also far more attractive to butterflies, 

 because their honey, inaccessible to humble-bees, is re- 

 served for them alone ; indeed, except some little Coleop- 

 tera, 1 observed only Lepidoptera visit the flowers of this 

 Alpine species of Primula,* whereas the flowers of Pri- 



52. Fig. 53. 



nulla officinalis are adapted by their dimensions to the 

 visits of humble-bees, and are actually visited by them.* 



A third example of the same relation between Alpine 

 species and those from the lowlands is presented by 

 Rhinanthus alpiniis (Figs. 51-56), as compared with R. 

 crista gain (Fig. 57). R. crista galli, which grows in 

 the plain and lower mountain region, presents two 

 varieties or sub-species : a, major, and [i, minor, with 

 difterent forms of flowers ; major with mjre conspicuous 



Fig. 54- 

 T\r.^. ii-ib.—Rhmantliits rtlf inns.— Vic. 51.— Lateral 

 another young flower, somewhat more full-grown, \ 

 older flower viewed Literally. Fig. 55— Front vii 

 anthers reserved. Fig. 57. — Rtti. 

 All figures are 3! times n.itural 



derlip ; a', longer .':tamens ; a-, shorter stamens ; 

 pposed path of the proboscis cf butterflies. 



Fig. ss. Fig. 56. Fig. 57. 



lew of a young flower when still almost entirely enclosed in the calyx {ca). Fig, 52. — Corolla of 

 wed from beneath. Fig. 53. — The same corolla, longitudinally dissected. Fig. 54. — Corolla of an 

 of the same flower. Fig. 56. — Corolla of the same flower, longitudinally dissected, but all four 

 crista gnlli. /3 minor, 

 figures: — frt, calyx :;>/. upper petals, forming together the upper" lip ;/'/'/', under petals, forming 



, nectary ; li, honey : oz', ovary ; si, stig 



The dotted lii 



Figs. 53 and 56 signifies the 



ones which never fertilise themseves, minor with less 

 conspicuous ones regularly fertilising themselves, in case 

 the visits of insects are wanting (Nature, vol. viii., 



* Visitors of Primula Ttllosa. — (A.) Coleoptera : Aiil/ioliiiait excavalttin 

 Er., frequently, crawling without difficulty into the flowers and out of them. 

 (B.) Lepidoptera: Picris calUdice Esp., Zygtrnaexnlayts Rain, both sucking 

 persevcringly and flying from flower 10 flower.- Piz Umbrail, July 16. 

 1874. 



pp. 433-435). Both are adapted to cross-fertilisation by 

 humble-bees, which, inserting their proboscis into the 

 comparatively wide entrance of the upper lip {c. Fig. 57) 



* Visitors of Printiila o^cin,ilis.—(A.) Coleoptera : Meligcthes. (D.) 

 Diptera: Bombyliiis discolor Mgn., sucking. (C.) Hymenoptera, Apida; ; 

 .■int/ioplwrapitipesT., ? i , Bombus muscoruml^. p, both frequently suck- 

 ing : Andrena Ciuynnna K. +>, Ilnlictus cyliniiricus 1'". ? and Halictiis al- 

 I I'lpcs F. +>, collecting pollen of short-5tyled flowers — Thuringia, April i6, 1 87 i. 



