460 ORGANOLOGY. 



B. Germination. 



186. Germination (germinatio) has a very different significa- 

 tion in Cryptogamic and Phanerogamic plants. With the first, as 

 also with Rhizocarpece, it is the development of a single cell, sepa- 

 rated from the mother plant, to an entire new organisation ; a 

 process which corresponds in the greater part with the formation of 

 the embryo in the Phanerogamic plants. Of these processes we 

 know nothing further than what may be considered analogous to 

 the life of individual cells. That which is most difficult to explain 

 here is the same as in the Plumerogamia, namely, the reason why 

 the spores remain so long without exhibiting signs of vital activity. 

 In Phanerogamia germination is only the development of an already 

 organised embryo into the perfect individual. The continued 

 development has no essential difficulties; but the circumstance of an 

 inactive vegetation previous to germination is the reverse of this. 

 We find here the following circumstances take place. Together 

 with the gradual maturing of the embryo, its cells are gradually 

 filled with assimilated matters, as starch, oil, and mucus, and they 

 lose by degrees almost all their watery particles ; hence arises 

 a condition in which, on account of the failure of moisture, the 

 chemical changes, and with them the vital processes, are slowly 

 effected. This condition remains in different plants various periods 

 of time, and is capable of being with some of them prolonged for 

 even a thousand years, or more, without the seed losing its capability 

 of development. This tendency to development is not aroused by 

 some circumstances which would be sufficient to excite the actual 

 vital processes of the plant. Thus the seeds of the Cerealia will 

 endure exposure to water at 45 C., watery vapour of 60 C., in dry 

 air of 75 C., and in dry cold of 50 C.* That with the com- 

 mencement of germination, the accession of moisture, &c., gives 

 activity to chemical changes, is far less striking than is the fact, that 

 they have not already taken place; but no one has ever dreamt of 

 discovering the cause of this latter. 



The phenomena of germination are as follows. The coverings 

 of the embryo (the testa, and, where present, the albumen and peri- 

 carp) swell up under the influence of water pressing in ; then the 

 cells of the embryo become distended, at first especially those of the 

 radicle and the lower part of the cotyledons (called cauliculus) ; by 

 this means the radicle is forced from the bursting seed, it sinks into 

 the soil, and whilst fastening itself in it, the slight curve of the 

 axis is removed by the distension of the cells lying on the concave 

 side, and the embryo erects itself above. The distension of the 

 cotyledons then forces off the coverings, which at length fall away, 

 and the free young plant grows unimpeded. Usually in Mono- 

 cotyledons, and occasionally in Dicotyledons, as, for example, in 

 Nymph&a, Quercus, jtEsculus, &c., the inferior part of the cotyledons 



* Edward and Colin in Ann. des Sc. Nat., 2d ser. Bot. i. 



