TIM': sr\i)i-:w a r.K'rrisii ixsixt-hatixc. plant 



r.\ I. IlMloKD Dl Dl.l \ lU XION anm I'llII.I 



r.AkKMl). F.E.S. 



Tliosic who arc fund of dabbling in old books as 

 well as searching out flowers in the field, will find 

 the subject of our pajier thus described by the 

 botanist Kay : — " Sundew, or Rorella, of which the 

 distinguishing marks are: the leaves are fringed all 

 round witii reddish bristles, to which little drops, as 

 it were of di'w. stick, etc."* 



Curiously enough, this keen old observer does not 

 mention the fact to which most people owe their 

 interest in the plant, namely, that it is carnivorous. 



It is customary to make the rough generalization 

 — inaccurate often in detail, though true in principle 

 as so many generalizations are — that plants can 

 feed on inorganic substances while animals need 

 organic food. This may be briefly explained as 

 follows: — We are all familiar with the old division 

 of the world into animal, vegetable, and mineral. 

 If we include under mineral everything, such as air 

 and water, which is neither animal nor vegetable. 

 we shall have the matter clear. Organic is animal 

 and vegetable, inorganic is everything else, .\ninials, 

 then, need organic food : plants can. with some 

 excei)tions, do without it. from wliich it follows that. 

 whereas plants could li\c witJKuit animals, animals 

 could not live without plants. 



But if we turn to the Sundew we are imme(liatel\- 

 confronted with an exception, a plant, which has so 

 far forgotten w hat is the usual nature of plants, as to 

 feed on meat. 



The time has gone past when science was allowed. 

 or indeed expected, to ask "win'," but it is our dutv 

 to ask " how." 



Now it will be noticed that the three ISritish 

 genera of insect-eating plants, viz., Drosera (Sundew), 

 Pinf>iiiciila (Butterwort), and Ufriciilaria (Bladder- 

 wort) live in marshy districts. It is probable that 

 to live in marshes and stagnant pools is to be in a 

 place where starvation is always a possibilitv. These 

 plants have found a method of getting out of the 

 difficulty by adopting, partially or entirely, a new- 

 diet. But to digest new food materials new methods 

 were necessary, and it is a curious fact that the 

 Sundew manages to digest the animals it captures in 

 a way not unlike that in which we ourselves digest 

 food. 



Trom this we may deduce the interesting fact 

 that a similar problem is solved in a similar \\a\-. 

 Such a condition is of special interest at the 

 present day, because of the various evolutionary 

 theories that are being put forward. It is said bv 

 some writers that every living thing has in it main- 

 possibilities which are not alwavs fulfilled, and that. 

 given the same circumstances, it is possible for li\-ing 

 things, though of widely different classes, to solve 



the same probleiiis in preciselv the same way. The 

 Sundew is an instance which might be adduced as a 

 case in point. There are, of course, many objections 

 to the theorj-. 



Let us now- consider the Sundew in detail. The 

 photographs here reproduced were all taken from 

 the same leaf at intervals and are enlarged twice 

 natural size. 



It will be seen (from I'igure 1.S4) that the leaf is 

 furnished with a large number of specialized hairs. 

 Each one bears at the extremitv a gland which is 

 very sensitive to the slightest touch, and which 

 secretes a drop of sticky fluid. It is possible that 

 insects when in want of moisture visit the plants in 

 the hope of satisfying their thirst, being attracted 

 by the drops of fluid resembling dewdrops, but 

 when once the\- have touched the leaf they are 

 usually unable to disentangle their limbs from the 

 sticky substance. The insect in its endeavours to 

 get free is almost certain to touch some of the other 

 hairs, and these help to hold it until it is hopelessly 

 entangled. If we watch very closely, we shall see 

 in a few moments that the hairs, which have been 

 touched, begin to bend inwards towards the middle 

 of the leaf carrving the insect w ith them. Soon the 

 imfortunate captive is brought into contact with the 

 next row- of hairs. These in turn bend, carrying it 

 further inwards, until it is in the middle of the leaf 

 and in contact with the short hairs of the central 

 disc. (See Figures 188-191.) 



Then from the last-named some sort of impulse 

 radiates to all the other hairs, and soon the insect is 

 clasped from all sides and enveloped in the secretion. 

 (See Figures 192-195.) 



The length of time which this takes varies con- 

 siderably, from under one hour, to as many as 

 twenty-four or e\-t'n longer, and depends on the 

 age and consequent vigour of the leaf, the tempera- 

 ture of the atmosphere, and many other circum- 

 stances. 



An insect, however, generalK" dies in from fifteen 

 to thirty minutes owing to its breathing tubes 

 (spiracles) becoming clogged with the secretion. 



A leaf usually remains closed over a fly for some 

 da\-s, then slowly re-opens, exposing to view the 

 harder parts of the insect, which have not been 

 digested. All secretion then dries up for a time and 

 the undigested parts drop off, or are blown awa\-. 

 Then the leaf again begins to secrete in readiness 

 for another meal. 



It is frequently stated that it is not possible to 

 deceive this plant, and that it w ill take no notice of 

 little jiieccs of stone or similar objects if they are 

 l)laced on the hairs. This, however, is not always 



Kos solis sen Korclla, cuius iiotae folia setis rubentibus circuin quaiiue fiiiibii;U;i quibus ^uttulao rclut roris ailliaerent. 



and so on. — Ray, " Ntetliodus Plantaruni." 



166 



