DIFFERENCES BETWEEN SPORES AND SEEDS. 



753 



be expunged from scientific language ; it may be translated seed-leaves. It is 



simply bad taste however to speak of them as seed-lobes. 



The rest of the drawings in Fig. 437, concerning which the explanation of the 



figure gives further information, show how the germ-plant (the embryo) contained 



in the seed, then developes further ; 



how first the root w and then the 



primary shoot-axis x elongates and 



emerges from the seed: the radicle 



enters the soil, the cotyledons c still 



remaining enclosed in the endosperm, 



to absorb the nutritive materials there 



stored up. It is not until this has 



been accomplished, and the ex- 

 hausted endosperm is reduced to a 



mere membrane that the plumule 



elongates upwards, and the coty- 

 ledons are withdrawn from the coats 



of the seed. 



After these preliminary explana- 

 tions, it is scarcely necessary to point 



out more particularly how great is 



the difference between reproduction 



by means of ordinary spores on the 



one hand and by means of seeds 



on the other. In the former case 



individual cells — i.e. the spores 



— become separated off from the 



mother-plant, and the new plant- 

 life begins, so to speak, entirely 



anew. Here in the case of the 



seed-plants the seeds also separate 

 from the mother-plant, of course, 

 to carry on a new plant -life, 

 but the young plant is already 

 there, and, in most cases, already 

 consists of the first rudimentary 

 organs, a primary shoot and radicle, 

 and these organs are composed of 

 innumerable minute cells in which 

 the tissue-systems are already dif- 

 ferentiated. The young plant which 



lies in the seed is already formed while the seed itself is still part of the parent 

 plant, and is so far nourished by this that subsequently, on the germination of 

 the seed, little more than a mere enlargement of the embryo is necessary. Seed- 

 plants may therefore in this sense be compared with viviparous animals. A 

 comparison of the Cryptogams or spore-plants with oviparous animals, however, 

 [3] 3C 



Fig. 6,-^T.—Pinus Pinea. I median longitudinal section through the 

 seed, J* being the micropyle end. // commencement of germination, the 

 root emerging. /// conclusion of germination, after the endosperm has 

 been exhausted (the seed was not deep enough in the soil, and was there- 

 fore carried up. by the cotyledons as the stem elongated). A shows the 

 ruptured testa atj-. B shows the endosperm f after the removal of one half 

 of the te&ta. C longitudinal section of endosperm and embryo ; and D 

 transverse section of the same, at the beginning of germination ; c coty- 

 ledons ; w primary root ; x the embryo-sac pushed aside by the root (it is 

 ruptured at Bx); kc hypocotyl; tu' secondary roots; r red membrane 

 lining the hard testa. 



