WHAT CONSTITUTES A FERN. 



and their perfeft form ; while in others, again, as in one of our N. Z. scale insects, the 

 male animal passes its whole life within the body of its parent, and thus till lately- 

 escaped discovery. Creatures, too, which were formerly supposed to be utterly dis- 

 tinct turn out to be earlier or later stages of the same thing ; and the discovery of 

 what is called " the alternation of species" has solved some of the difficulties. In the 

 case of most of our garden flowers and cultivated fruits, the male and female organs 

 are contained in the same blossom ; an arrangement which tends to promote fixity of 

 type through successive generations, varied only bv accidental or intentional hybridi- 

 sation. In some cases, however, such as melons, cucumbers, pumpkins, nuts, conifers, 

 &c., the male and female organs are situated in separate blossoms on the same plant : 

 and in others, such as hops, some of our N. Z. forest trees, and one of our grasses, the 

 male and female flowers actually grow on separate plants. In both these last cases, 

 the pollen (fertilising dust) of the male organ of the one blossom has to be carried by 

 the wind or by insects to the female organ of the other, in order that the latter may 

 be fertilised and the fruit be developed. In the cryptogams, however, no male or 

 female organs could be discovered ; and though reasoning from analogy, it was inferred 

 that the bi-sexual law applied to them also, where it came in or how it operated was a 

 mystery ; and hence the term cryptogam. It is only of late years that, by persistent 

 microscopic observation, the mystery has been solved, and the extraordinary discovery 

 made that the spores (supposed seed) of cryptogams are actually the germs of 

 blossoms which develope after leaving the parent plant, though germs of all other 

 blossoms would die if similarly removed. Spores of ferns are so minute as to be 

 hardly distinguishable by the naked eye, unless in large quantities, when they appear as 

 reddish brown or black dust ; or, in autumn, as a reddish brown scum upon water. Seeds 

 produce plants directly : spores do not. All true seeds contain a tiny germ which 

 developes into the future plant, but the bulk of their mass consists of food for that 

 plant in its early stages ; in, fact, a seed is a vegetable &gg. When subjected to the 

 requisite conditions of heat and moisture, a seed swells and bursts its skin or shell. 

 The germ then protrudes and sends roots downwards ; and when these have got suffi- 

 cient hold to sustain the young plant, it begins to push its way upwards, usually 

 carrying the food store up with it in the form of seed-leaves, which not only supply 

 nourishment themselves but gather a farther supply from the atmosphere. Nothing 

 of the kind, however, occurs in the case of the spore of a cryptogam, which is a mere 

 cell of vegetable matter without any interior germ or separate food supply ; and which 

 seems to have the power of growth all over it and in any direction according 

 to circumstances. It sends down no true roots, but either lies loosely on the 

 ground or other substance on which it falls, or adheres to it merely by some slight 

 viscosity or a few root hairs. Spores of ferns seem to grow better on steep or 

 inclined surfaces than on horizontal ones : for in a fernery, far more young plants 



