54 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



should be to ascertain exactly what the structure is, and then 

 to build upon the observation ; but to place no superstructure 

 whatever on facts which admit of two distinct interpretations, 

 one of which is as plausible as the other. A great degree of 

 caution is wanted, and of good faith too, without which error is 

 inevitable where such dehcate and precarious manipulation is 

 required. The Cryptogamic student, if he enters on more than 

 the mere determination of species, will find enough to call for 

 the exercise of no ordinary acuteness. Let him, for instance, 

 strive to ascertain exactly the nature of the communication 

 between the plant and matrix in the parasitic fungi, which 

 belong to the group of rusts and mildews, and he will soon find, 

 if he is wise, that he cannot well be too cautious before he 

 draws his conclusions.* 



40. A few words must still be said about Cycads, both on 

 account of the remarkable fact of the circination of the pinnate 

 leaves in many species, and of the deviation from the normal 

 venation of Zamice in Stangeria (Fig. 1), resembling perfectly 

 that of ferns. That there is a resemblance in the vegetative 

 organs here is undeniable, as there is in those of Podostemads 

 to HepaticcB, or of Balanophorce to Fungi ; and were this 

 accompanied by changes in the fruit at all approximating it to 

 that of Cryptogams, it would have considerable weight. We 

 have, however, as distinct a dicotyledonous embryo in 

 Cycads, as in any Exogen, and perfect pollen. The sper- 

 matozoids of Acrogens are so totally different from this 

 latter, and the whole history of their vegetation, that, in 

 spite of one or two points of resemblance, and those not 

 universal, I cannot see here, again, anything approaching 

 to afiiuity, though there is a foreshadowing of structures to 



* la books intended for students, an author cannot be too sure of 

 the facts which he lays before them ; nor be too severe in his application 

 of them. Otherwise his reader will throw down the book in despair, 

 since he can obtain no definite notions from it, or will gradually fall into 

 the same loose way of reasoning himself, and derive no lasting benefit 

 from it. He may cram up its contents for examination, and when they 

 have answered that purpose, they will be put out of mind for ever. 

 He will, in ftict, have acquired nothing solid ; nothing that can help 

 him to the acquisition of fresh knowledge. 



