BOTANICAL SUBJECTS. 275 



In what does the stem of a Tree Fern differ from the stem of 

 a Cycad and a palm ? The cryptogam and phsenogam differ no 

 doubt, and more so, perhaps, than the horse differs from man; but, 

 morphologically speaking, I cannot see that they are so distinct 

 tliat it would be absurd to consider the spore and the Citrus 

 embryo as morphologically one and the same thing. When there 

 is only one embryo in a Citrus seed, it would appear to mean that 

 all the spores or embryos but one have been suppressed. 



The spore and the embryo are both unicellular, and the difference 

 between them, at a certain stage, appears to be this : The former 

 is fitted to live an independent life while it is still in its 

 unicellular stage, while the latter has to develop itself further 

 under the nursing care of its parent, and become a bud with an 

 incipient radicle and provided with a store of nourishment in 

 its bud-scales (cotyledons), before it becomes fitted to lead an 

 independent life. 



We have become so accustomed to see beautifully formed and 

 coloured flowers, that the form, colour, and splendour strike us as 

 being of paramount importance, but every schoolboy now knows 

 that the essential parts of a flower are the pollen and ovules, that 

 is, the male and female elements.* 



When the fern spore germinates, it begins its life by producing 

 a rudimentary flower, with male and female elements — the 

 so-called jjrothallus. After the sexual union, the ovule of the fern 

 develops into a bud — homologous with the bud of a seed — which 

 grows into the plant, and after a certain further growth, the 

 process of disseminating spores recommences. 



In phaenogams there are many stages before the flower 

 containing the sexual elements appears. The ovule after 

 fertilization grows into a special form of bud, which we call the 

 seed. When, under favourable circumstances, it develops further, 

 a number of leaves and stem have to be formed before the sexual 

 parts appear. These appear later or sooner, very often as the 

 surroundings tend to luxuriance or to starvation. 



Then the difference between them is that the spore changes at 

 once into the sexual parts, while the embryo has to go through a 

 more elaborate process before it does so. 



* The modem view of colours and forms of flowers of course is that they 

 are connected vrith insect and bird life. 



s J, 



