INTRODUCTION TO CRYPTOGAMIC BOTANY. 61 



Leontice there are two cotyledons -with, however, a similar 

 formation of a tuber. In Linaria arenaria, a shoot is formed 

 below the cotyledons, a circumstance which has been observed 

 also in Euphorbia Lathyris, and some other species. In 

 Cyclamen the germination is that of Dodecatheon, but only 

 the petioles of the cotyledons are developed. 



49. It would be easy to multiply such examples to almost 

 any extent, were it necessary to do so. I shall, however, still 

 point out one soiu-ce of fallacy in the estimation of affinities, 

 which arises from the extreme difficulty of appreciating them 

 till the real clue is found out. Fries, indeed, has shown a 

 wonderful tact in ascertaining the affinities and nature of cer- 

 tain Fungi, but till the true structure of the hymenium was 

 known in the Puffballs, Stinkhoms, Birdsnest Pezizas, and a 

 multitude of other instances, it was almost impossible to ar- 

 range them in any natural sequence. The true affinities of 

 such genera as Nidularia and Sphwrobolus, could never have 

 been imagined without some such clue. The same may be said 

 again of the naked-seeded truffles ; nothing is more clear than 

 their real nature, now that the structure of the hymenium in the 

 higher Fungi is known ; and as regards the truffles with 

 inclosed spores, the discovery of Genea, and much more of 

 Hydnoeystis, which is a mouthless Peziza, at once makes the 

 passage from Tuber to Peziza evident, the one having the 

 rough sporidia of P. radula, the other, the smooth sporidia 

 of P. arenaria, which is almost hypogeous. Who could 

 guess, at the first glance, or, indeed, without a knowledge of 

 the fruit, that there was any affinity between Callitriche, 

 Hippuris, and Onagrarice, or, much more Myrtles .? Take 

 again the affinity of Lemma and Arum. There is not the 

 slightest external sign which could lead to a notion of affinity, 

 and the whole structure of the plant is against such a notion. 

 The genus Pisiia, however, on the most superficial glance, 

 indicates an affinity with Lemmn. The habit is the same, and 

 there is the same highly-developed pileorhize, which is no 

 special organ, but the same thing with the pileorhize in more 

 complicated plants. The inflorescence is, however, no longer 

 so thoroughly simple. There is a distinct spatha, and a cup- 



