PLATE XXVI.— PARASITES AND INSECTIVOROUS PLANTS. 



In a work dealing with typical forms of plant-life it would be unpardonable entirely to overlook the subjects of the present Plate. 

 They are not treated, however, with great fulness, because the object in view was rather to call attention to them, than to make a 

 detailed study ot them. I have endeavoured to represent them in such a way that they may be easily recognised when met wit.i, and 

 carefully examined. 



In the case of Insectivorous Plants, students often either do not know them or overlook them from their relativelv sma'l size. 

 They are accustomed to such magnified drawings and have such exalted notions of Traps, Tentacles, and Bladders, that the little 

 Sundew of our moors, for instance, is hardly within their range of vision. To obviate this, each plant or a conspicuous portion of the 

 plant is given in its natural size. The three British genera here figured were all obtained from around Edinburgh— Sundew from the 

 neighbourhood of Balerno, and Butterwort and Bladderwort from Gullane— and the little that is given about them may tempt the 

 student to seek further information in the late Mr Darwin's well-known work on "Insectivorous Plants." 



The mode of Nutrition is the principal thing to be noted in each case, and it will be seen that not merely living and decayed 

 /egetable matter may be absorbed by plants, but even digestioti and absorption of living and decayed animal matter can be accomplished. 



Mistletoe (Viscum album). 



The Mistletoe with its berried Fruit is a familiar object at Ch istmas-time, but it is in summer that the Flower is met with. It 

 is parasitic on trees, such as the Apple and Hawthorn, but rarely on the Oak. The berries are used for making bird-lime, hence the 

 name of the plant Viscum (Lat viscus, bird-lime). The seeds are often sown on the branches of trees by birds, which eat the fruit for 

 the sake of its succulent and viscid cover, and afterwards cleaning their bill, leave the seed behind sticking to the tree. The seed 

 begins to germinate generally after it has slipped round to the under surface of the branch, and puts forth rootlets which bore through 

 the bark and pass towards the centre along the softest parts — the medullary rays. It thus becomes blended with the tissues of the 

 plant on which it grows, and by means of this organic connection feeds upon it, frequently killing the branch on which it has settled. 

 The Mistletoe is a parasite which does not live wholly at the expense of others, but does something for itself by means of its green 

 leaves. The Dodder (Cuscuta), however, produces no leaves, not even seed-leaves, but twines round its host— such as the Clover and 

 sucks the substance out of it. There are plants even, such as the Bird's-nest Orchid (Neottia), which grovel in decay, and live upon 

 decayed vegetable matter, such as decaying leaves and the like. Such are distinguished as Saprophytes (Gr. sapros, rotten ; phuton, a 

 plant). 



Fig". 1. Branch of Fir-tree, in section, showing sucking roots running through it 



Figs. 2 and 3. Male and Female Plants distinct. 



Male Inflorescence consists of three flowers, each flower having usually four Perianth-leaves, and the sessile 

 Anthers inserted upon them. 



Female Inflorescence also of three flowers, each with four Perianth-leaves and a relatively large inferior Ovary. 

 Fig. 4. Fruit, a berry, easily cut through. 



The fruit-cover is pulpy and sticky, and the single seed frequently contains more than one embryo, usually two, 

 embedded in the endosperm. 



Bladderwort (Utricularia— Lat. Utriculus, a little bottle). 



(Fig. 8 after Cohn). 



Bladderwort occurs in stagnant water and in ditches which are foul and therefore swarming with minute animal life. It flowers 

 about July. 



Figs. 5 and 6. The flowering stem rises above the surface of the water and bears a few yellow flowers. The flower has an 

 upper and an under lip, with a well-marked prominence on the latter, and altogether has a general resemblance to the 

 flower of Snapdragon. 



Fig. 7. The Leaf is much divided and the divisions continually fork. The Bladders are borne on short stalks and vary in 

 number. 



Fig. 8. The Bladder consists of a transparent membrane, and the specimens examined were of a pale, purple tint. Small animals, 

 such as Cyclops, Insect larvae, etc., gain admission by following the bristles at the entrance, and thereby opening a 

 folding door in the shape of the free edge of an elastic valve ; this shuts after them so that they are entrapped. The 

 Bladders do not secrete, but only absorb, the decayed matter by means of four-armed processes covering the interior. 



May. 



Butterwort (Pinguicula vulgaris— Lat pinguis, fat). 



Butterwort grows in damp places, sometimes near to the stagnant waters containing Utricularia, but flowering earlier, usually in 



Figs. 9 and 10. One or more stalks arise from the centre of the radical leaves, and each bears a terminal drooping, violet 

 flower with a projecting spur. 



Fig. 11. The leaves have usually incurved margins and are embedded in the boggy ground, so that they are on a level with 

 the surface, and creeping things may readily get on to them. When plucked up by the root the leaves soon bend 

 back and almost meet by their tips, and this folding is the same which keeps them flat when growing. 



Fig. 12. Bend a leaf about the finger, and remove a thin portion of the surface with a sharp razor, and examine to see the 

 glands on the surface 



There are two kinds of glands — those which stand out on a stalk and those which are sessile These glands 

 secrete a viscous fluid, and when small flies, etc., venture on the leaf, the margins arch over them, and the secretion 

 acts upon them until they are dissolved. Here a process of digestion takes place 



Drosera rotundifolia (Gr. drosos, dew). 



The Sundew derives its name from the glistening appearance of the fluid drops at the tip of each of the tentacles of the leaves. 

 It occurs on boggy ground and wet moors, and the moss serves as a sponge to keep up a supply of water. It flowers about July. 



Fig. 13. The Leaves are arranged in the form of a rosette, and the scape bearing several flowers has a characteristic bend 

 towards the top. The flowers are comparatively small, and the white petals are almost enclosed by the sepals, 

 merely peeping forth a little at the top. 



Fig. 14. The Leaf is beset with numerous Tentacles, each terminated by a gland, and surrounded by a colourless viscid 

 secretion. An insect alighting on the centre of the leaf is speedily enveloped by the infolding tentacles, and the 

 copious secretion poured forth by the glands not only weakens its struggles but shortly smothers it. Thus quietly 

 resting on the leaf which forms a trough for its reception, the soft parts of the insect are gradually dissolved and 

 absorbed by the Leaf, which again expands its tentacles to glitter in the sun and attract more prey. 



