STUDIES IN VEGETABLE PHYSIOLOGY. 



and from the branches, as in the Banyan. Moreover, this tendency to shoot in the air is 

 shown even in the embr^'-o, which begins to germinate while the pod is yet attached to the 

 parent branch; the radicle, or root end of the embryo, elongating into a slender thread, 

 which often reaches the ground at the height of many yards, before the pod is detached. 

 In this manner the Mangrove forms those immense maritime thickets which abound on low 

 muddy shores within the tropics. There is a class of plants called Epiphytus or air 

 plants, which exhibit a further peculiarity. They not only emit roots from every 

 part of their trunks, but during their whole life have no connection with the soil; they are 

 generally found growing upon bark, and the trunks of old trees. The roots adhere to the 

 bark, and fix the plant in a steady position, or else hang loose in the air, from which such 

 plants draw all their nourishment. The parasites are mostly natives of southern regions, 

 such as the orchidaceous plants; many of them adorn our hot-houses, and are rare and 

 interesting objects. Some parasites not only grow upon other plants, but live wholly at 

 their expense, which the epiphytes do not. Parasites may be reduced to two different 

 sorts: first, green parasites, those which have green and proper foliage for respiration and 

 perspiration — and second, those which are destitute of green foliage; they also differ in 

 their degree of parasitism — the great number of them oeing dependant upon the foster 

 plant for support; but there are a few, such as the Colutiarosea, which often take root in 

 the soil, and from thence assimilate a part of their food, and in some cases live and grow in- 

 dependent of their aerial roots. The green parasites are furnished with proper digestive or- 

 gans of their own, just as in the higher class of flowering plants; they strike their aerial 

 roots through the bark of the plant upon which they grow, and embed themselves in the 

 alburnum, from which they can draw little or no sustenance, except the crude ascending 

 sap, which they must assimilate with their own organs. The Misletoe is always parasitic, 

 being at no time connected with the soil; the seed germinates upon the tree wherever it 

 happens to fall; the germinating root, or the woody mass which it forms resembling the 

 root, penetrates the bark of the foster plant, and forms a close junction apparently, with 

 its young wood, as that of a natural branch. Some species of the Misletoe have no pro- 

 per green colored foliage, but are of a brown or yellow cast. Pale or colored parasites, such 

 as the Beech drops, strike their roots in the bark of the foster plant, and thence draw 

 their nourishment, already assimilated. Hence they have no use for their proper colored 

 foliage. In some instances, such plants as the Dodder will germinate in the earth, but as soon 

 as they grow large enough they twine around some approximate tree, their aerial rootlets pe- 

 netrating the epidermis into the bark, and feed upon its nourishment — while its own root 

 dies, and the plant has never any more connection with the soil; thus the plant, like some 

 human ones, steals its nourishment, and requires no proper foliage, for it would not use 

 it if it had it. Such parasites do not live upon all plants, but only upon those which 

 will yield a propitious food. Some, it is said, are restricted to certain species, and others 

 seem to have little or no choice. Their seeds are only germinated when placed in contact 

 with the plant upon which they are to grow. Some parasites may be reduced to a single 

 flower, or flowers, situated immediately upon the foster plant. A truly wonderful instance 

 of this kind is furnished by that vegetable titan, the Rafflesia arnoldi, of Summatra. The 

 flower which was first discovered grew upon the stem of a kind of grape-vine; it measur- 

 ed nine feet in circumference, and weighed fifteen pounds. Its color is of light orange, 

 mottled with yellowish white. Some cryptogamous plants, such as the fungi, are parasi- 

 tic upon languishing vegetables, and some infest living animals; the rest live upon decaying 

 animal and vegetable matter, and are all destitute of clorophyle, (coloring matter.) 



Augustus A. Fahnestock 



