VEGETABLE IRRITABILITY. H 



vessel of sea-water. Then ocoviis a series of most curious phenomena. 

 The antherozoids attack the spores, creep, as it were, over their surface, 

 and communicate, by means of their vibratile cilia, a rotatory 

 motion, which is sometimes very rapid. "Nothing," says M. Thuret, 

 "is more curious than the appearance of great brown spores rolling and 

 tumbling about in the midst of a swarm of antherozoids." The result 

 is the fertilisation of the spore, which then begins to grow, and in ten 

 days becomes a little cellular brown oval body, supported by a trans- 

 parent rootlet. Sea- weeds are by no means the only plants in which 

 these most remarkable phenomena have been detected. Most cryptogamic 

 plants have now been observed to possess locomotive organs, analogous 

 to antherozoids and bearing the same name. Liverworts, Mosses, 

 Lycopods and Perns themselves are supplied by nature with parts of 

 the same description. When a Fern-seed vegetates it forms a small, 

 thin, two-lobed green plate or scale lying horizontally on the damp 

 surface of the ground. In this scale, called a protothaU, lodge anthero- 

 zoids and spores. By unknown means the former creep up to the latter, 

 and fertilisation is accomplished. Wherever Fern-seeds have fallen, 

 there a crop of these scaly protothalls springs up, as may be seen on the 

 walls, or pots, or damp earth of any Fern-house. In each protothaU. is 

 lodged an abundance of antherozoids and spores, the former active and 

 capable of moving from place to place, the latter passive and stationary. 

 Nor is there any thing in their structure which enables the observer to 

 say whether the motions are voluntary or involuntary, so much do they 

 resemble what is witnessed in animal life. 



So far then as the important phenomena of reproduction are con- 

 cerned, we have indications not only of vitality, but of such a force 

 being present in plants in great activity. 



Evidence of this kind, proving as it does beyond all 

 doubt the presence of a vitality among plants identical with 

 that of animals, though different in its manifestations, is greatly 

 strengthened by the many known cases of what is called 

 vegetable irritability. 



That of the Sensitive Plant, which shrinks from the touch ; of the 

 OsciUating Saintfoin (Hedysarum gyrans) whose leaves move with as 

 much appearance of spontaneousness as the polype ; the sleep of leaves 

 and flowers which close at night and expand in the day; the violent 

 recoil of the column of Stylidium, or of the lip of Draksea, when 

 touched ; the oscillation of the labellum of many BolbophyUs and 

 Pterostyles ; the snap of the traplike leaf of Dionsea which closes 

 with great force whenever' one of its six bristle-shaped springs is 

 disturbed — phenomena familiar to the naturalist — are all intelligible 



