263 



HARDWICKE'S SCIENCE-GOSSIP. 



[Dec. 1, 1S6S. 



with no unmeaning finger, along the track we have 

 to look for the unfolding of that mysterious connec- 

 tion that obtains between the present and the past 

 forms of animal and vegetable life. 



Many common plants, generally regarded as well- 

 defined species, are found on closer examination and 

 more careful study to be little less than small genera, 

 or at least groups of varieties or races. In the face 

 of such facts as these, what certainty have we that 

 many plants, now justly regarded as species because 

 found to be permanent forms, are not mere varieties, 

 from closely allied species, of some centuries' stand- 

 ing? There seems nothing extravagant in this 

 notion; yet were a few cases of the kind clearly 

 proved, they would speak volumes. Such proof, 

 however, is almost impossible from the fact that 

 varieties have not heretofore been clearly marked 

 out and defined. Future naturalists will have more 

 data to work upon, and may thus be able to prove 

 the origin of species by variation experimentally. 



As a case of this loose definition, we will instance 

 the common Hawthorn {Crategus oxyacantha) . 



Mr. Hobkirk, in the year 1866, drew the attention 

 of working botanists to this plant in the pages of 

 the Naturalist. After a considerable amount of 

 laborious research, and many examinations of fresh 

 and dried specimens, he arrived at the conclusion 

 that we had in England at least four well-defined 

 varieties. These he described under the names of 

 Crategus oxyacanthoides, C. monogyna, C. kyrtostyla, 

 and C. laciniata. During the summers of 1S67 and 

 186S I have myself given much time and attention 

 to this plant. I find three of the forms well marked 

 and abundant in this neighbourhood. I am not so 

 clear about the fourth, C. laciniata, though I have 

 found many specimens that I believe to be referable 

 to it, but accompanied by many intermediate forms. 



Fig. 24S.— Leaf of Crategus oxyucanthoides. 



I will attempt to describe them for the benefit of 

 those whose attention may not already have been 

 directed to them. The descriptions have in every 

 case been drawn up from the examination of fresh 

 specimens, many hundreds of which were passed in 

 review for that purpose. 



1. Crategus oxyacanthoides. — Styles 2-3 (rarely 

 in a few flowers 1 only). Calyx and peduncle quite 

 glabrous. Calyx-teeth short, triangular, spreading 

 (never reflexed either before or after flowering), 



united by a small membranous border. (As seen 

 from below, the calyx is regularly pentagonal, the 

 angles very [slightly projecting — fig. 249.) Leaves 

 rather small roundish, or obovate ; three or five not 

 deeply cut lobes, generally copiously serrate ; nerves 

 distinctly converging (fig. 24S). Petioles pubescent, 

 also nerves of leaves and midrib, below, slightly 

 hairy above. The base of the leaf and of each lobe 

 generally sub-ciliate. 



Fig. 250. 



Fig. 249 



Fig. 251. 



The mere inspection of the foliage alone is mostly 

 sufficient to determine this species. It has a very 

 different appearance from the other varieties. The 

 leaves are smaller, much less deeply cut, of a lighter 

 green, and not so highly polished. 



2. Crategus monogyna.- — Style 1. Calyx and germen 

 glabrous ; calyx-teeth oblong, reflexed, generally 

 shorter than in Kyrtostyla. Leaves glabrous on both 

 sides, except base and principal veins, which are 

 sometimes sub-ciliate ; three or five somewhat 

 deeply cut lobes. 



3. Crategus kyrtostyla. — Style mostly 1 (some- 

 times 2), generally more or less incurved. Calyx, 

 germen, and extremity of peduncle covered with soft 

 silky hairs. Calyx-teeth lanceolate obtuse, as long, 

 or nearly as long, as germen, upon which they are 

 closely reflexed (fig. 250). Leaves rather large, deeply 

 three- or five-lobed ; summit of lobes more or less 

 serrate ; petioles, base, and inner side of lobes of leaf 

 sub-ciliate ; glabrous on both sides, except midrib 

 and principal veins, which are very slightly hairy 

 (fig. 252, leaf of C. kyrtostyla). 



4. Crategus laciniata. — Style 1, erect. Calyx, 

 germen, and peduncle glabrous. Calyx-teeth lanceo- 

 ate, acute. Leaves pinnate, lobes very deeply cut, 

 first generally to midrib, and others nearly so ; large, 

 dark shining green above, strongly inclined to grey 

 beneath (fig. 253, leaf of C. laciniata). 



Between two of these forms, C. kyrtostyla and C. 

 monogyna, I have noticed a considerable number of 

 intermediate forms, but the varieties themselves arc 

 well marked and easily distinguished. C. oxyacan- 

 thoides, as will at once appear from the descriptions 



