10 MANIFESTED BY POLLEN-TUBES, ETC. 



entranoe of the pollen- tube into the young seed through its foramen,* is 

 assisted by movements on the part of the seed itself, as in the common 

 garden Thrift ( Armeria) in -which a horizontal strap, interposed between 

 the pollen-tube and the foramen, is spontaneously removed in order to 

 enable the former to enter the latter. These phenomena, varying as the 

 structure of plants itself varies, and destined as they evidently are 

 to ensure that great end, the propagation of species, are wholly inex- 

 plicable upon any other principle than that of high vitality ; so high 

 indeed that they are only less than voluntary actions. 



d. But perhaps nothing places the presence of a powerful vital force 

 in stronger evidence than the facts which modem botanists have 

 discovered in connection with the propagation of the lower orders of 

 plants. It has been known from the observations of the younger 

 Agardh, that in fresh-water Confervse the seeds (technically called 

 spores) swim about with activity in the interior of the cell which 

 generates them, that they eventually force their way through a thin 

 part of the cell waU, andthenoe darting into the water move about with 

 great activity, the lighter end downwards, and therefore contrary to the 

 force of gravitation. These motions last for several hours. More 

 recently it has been demonstrated that the motion is caused by delicate 

 vibratile cilia or fringes attached to the small and narrow end of the 

 seed (spore). This motion is stopped instantaneously by any poison, 

 such as iodine, being allowed to mingle in the water. Discoveries of a 

 similar nature have been made among other races of plants. Modem 

 research has shown that in the greater part of the lowest forms of 

 vegetable Ufe, and probably in all, minute spiral bodies exist having 

 the power of active locomotion in many cases. These are called 

 Aniheeozoibs in consequence of the bodies or antherids which contain 

 them being regarded as analogous to the anthers of the higher orders of 

 plants. Sea-weeds bear both spores and antherozoids. According to M. 

 Thnret, whose observations are not open to doubt, by placing certain sea- 

 weeds in a damp atmosphere, the spores and antherids are freely 

 expelled, and remain on the surface of the fronds, from which they can 

 be readily collected and transferred to vessels containing sea-water. 

 M. Thuret found that when put iato separate vessels, the antherids 

 placed by themselves immediately emit their antherozoids ; the latter 

 move about with great activity, even for two days successively, but on 

 the third, begin to decompose. Spores, also, when placed in sea-water 

 by themselves, retaiu their vitality for some time, not decomposing in 

 less than a week ; they even make attempts at growth, but abortions 

 are the only consequence, and at last they perish also. It is 

 otherwise when the spores and antherozoids are mingled in the same 



• The foramen is a mmute passage through the integuments of an ovule or young 

 seed, into which the pollen-tube must enter in order to vivify the latent embryo 



