HARD WICKE ' S S CI EN CE-GO SSI P. 



249 



struggling there : as, for instance, if its proboscis is 

 too short to reach the coveted nectar. It is most 

 amusing to watch a small humble-bee working at 

 Dclphiniuni, with a proboscis not long enough to 

 reach the nectar. With what rage he flies from one 

 ilower to another, until he finds out the best method 

 of getting at the nectar is to bore a small hole at the 

 Imck, or thrust his proboscis in a hole made by that 

 •energetic little depredator the ant ! 



Fig. 182. Flower of Delphiniitin. a, nectar-tube ; l>, front 

 petal ; c, pistils. 



Well, how is fertih'zation 



effected ? and in what way does 



the bee perform it ? To answer 



the question we must seek the 



position of the stigma. Let us 



suppose, then, we examine a 



,, flower where the first lot of 



183. 184. 



Fig. 183. Pistil when Stamens are shedding then- pol- 



the first anthers open, j ^^ ^^y ^^^^ ^^^ 3^^. 



Fig. 184. Pistil when \b J/ } 



all the anthers have mens, and we hnd the pistils 



'''"'''po^lfn. '^^'' quite immature, with scarcely 

 any style developed (fig. 183) ; 



iFig. 185. '^lowtr oi Delphiniuii!. «, upper petals (the front ones 

 removed) ; b, five stamens, erect and shedding their pollen. 



and it is not until all the anthers have discharged 

 their pollen that the pistils arrive at maturity, i.e., 

 with the style lengthened out so as to bring the stigma 

 within easyreach of the pollen (fig. 184). Well, what is 

 the advantage gained by such a delay in the develop- 

 ment of the pistils ? It is certainly for no other purpose 

 than that cross-fertilization may be effected ; and, to 

 secure that end, the stigmas are placed in precisely 

 the same position as that previously held by the 

 stamens (fig. 182, r). Thus, the bee which has become 

 dusted with pollen from newly-expanded flowers, 

 when visiting others which had been longer open, 

 would carry the pollen to the waiting stigmas ! It is 

 almost, if not quite, impossible for the stigmas to be 

 fertilized with the pollen of the same flower, and this 

 will account for the copious supply of seed always 

 produced upon Delphiniums in our gardens. It is 

 veiy difficult to imagine a more simple, and yet more 

 effectual arrangement to bring about cross-fertilization ! 



J. T. Riches. 



ON CERTAIN GENERA OF LIVING FISH 

 AND THEIR FOSSIL ALLIES. 



No. II. 



HAVING shown the close connection between the 

 two genera of living Dipnoids, let us now con- 

 sider the relations of the living and fossil Ceratodonts. 

 No remains of this genus have as yet been found in the 

 Tertiary or Cretaceous formations, but the fossil teeth, 

 of which several varieties are recognizable, possibly 

 the relics of numerous species, occur abundantly in 

 the Triassic beds of Aust Cliff", near Bristol ; in the 

 Stonesfield Slate of Oxford ; and in the Muschelkalk 

 of Gemian}'. They have also been obtained from 

 strata now determined to be of Triassic age at Maledi, 

 South of Nagpur, in India, and associated, as in 

 Europe, with the reptilian remains Hyperodapedon. 

 Many of these fossil teeth are much larger than those 

 of the existing species (specimens of one Triassic 

 form measure over two inches in length), and must 

 necessarily have belonged to individuals of a gigantic 

 race. The dental plates only have been found fossil, 

 but the stracture of Ceratodus Fostcri indicates that 

 they alone of a like-constructed animal would be 

 susceptible of preservation in sedimentary strata, and 

 the classification of the recent forms with those of the 

 Mesozoic rocks, separated by so wide a gulf of 

 geological time, though founded on the similarity of 

 the dentition alone, is the only reasonable one, as 

 there is no evidence that the living and fossil Cerato- 

 donts differed from each other. The teeth of this 

 genus resemble in general shape and structure those 

 of Ctenodns, -which are widely distributed in Carboni- 

 ferous strata, species occurring in America being 

 identical with those of the British rocks of contem- 

 poraneous age. The dentition of the Devonian 



