H 



Marvels of the Universe 



In spite of all these difficulties, the little Sundew (a distant relative of the common London 

 Pride) lives and flourishes amazingly among the sphagnum mosses on the peat bogs. How 

 it learnt to thrive so well where most other plants would perish, is not difficult to understand when 

 we remember that its remote ancestors were almost certainly saxifrages — a familj' of plants noted 

 for possessing sticky glandular hairs about their stems and leaves. If then the parent form of the 

 Sundew happened to be placed on peaty ground, and. as often happens with hairy plants, small 

 flies became entangled in the sticky hairs of its leaves and perished there, their decaying bodies would 

 render good service to such plants by supplying their tissues with those materials which the soil 

 lacked. In this manner the plant would benefit, and so those individuals which produced the most 



sticky and the most absorbent hairs 

 .^"s. about their leaves, would thrive best, 



and by a process of natural selection 

 the hairs would develop into complex 

 and sensitive glands capable of move- 

 ment and of secreting a digestive fluid. 

 An e.xamination of one of the leaves 

 with a pocket lens will show how it 

 contrives to obtain sufficient nourish- 

 ment. Its green surface is studded 

 over with numerous movable glandular 

 hairs of a reddish colour. The swollen 

 gland at the head of each hair glistens 

 in the sunlight as if fresh with moisture 

 from the morning dew — hence its 

 poetical name Sundew. The whole 

 structure of the newly-opened leaf 

 makes a charming object when seen 

 through a lens. But the great Charles 

 Darwin discovered some extraordinarj' 

 details about these tentacles of the 

 Sundew which leave no doubt of their 

 blood-sucking propensities. 



He has conclusively shown that 

 these glandular structures are of a 

 most complex character, and that 

 when the long external tentacles were 

 touched, or when placed in contact 

 with organic and inorganic substances, 

 they became inflected. If the object 

 adhering is a fly, the one or two tentacles engaged heave it into the centre of the leaf. The 

 moment the object so lifted comes in contact with the central area of the leaf, the glands there 

 affect the external tentacles so that they also slowly bend inwards. At the same time the blade of 

 the leaf will often become hoDowed, and so form a kind of cup in which the unfortunate caterpillar, 

 fly, or other prey, is held while the glands pour upon it their viscid fluid. It is obvious, therefore,, 

 that the more the quarry struggles the less chance it has of escaping, for, the more the glands are 

 excited, the more fluid do they pour out. 



A more curious discovery made by Darwin was that, when the tentacles were bent, this secretion 

 was changed into an acid. Now this was important, for the gastric juice of animals contains both, 

 an acid and a ferment, and so Darwin was led to inquire if the leaves of the Sundew really ate and. 



Pholn '>»] [/. /. Ward. 



A SUNDEW LEAF AND ITS CAPTIVE ANT. 



A microscopical photograph showing ho^v the tentacles approach, and. by 

 their sticky knobs, hold any insects that alight on the leaf. 



