HARD WICKE'S SCIENCE- G OS SIP. 



IT 



comparatively few specimens to be found, and none 

 in No. 2 section. In 1SS5, I found but three specimens 

 in No. 1 section, and again none in No. 2. 



In 1886, I could not find a single plant in No. I 

 section, although I paid several visits, and took with 

 me several good searchers ; but in No. 2 section I 

 found two plants. 



In 1S87 I was still unable to find any plants in 

 No. r, while in No. 2, which is now about six years 

 old, I found the plant in comparative abundance. Of 

 course, during the first few years following the cutting 

 down of a copse, the undergrowth is very considerable, 

 and the difficulties of finding so small a plant as 

 L. squamaria are great. But I feel convinced, from 

 my experience, that its appearance is influenced (like 

 that of some other woodland plants) by the condition 

 of the copse with regard to its undergrowth. 



That it has a most remarkable vitality, the following 

 (communicated to me by G. B. Wollaston, Esq., of 

 Chislehurst) will show. He informs me that he had 

 a plant of Z. squamaria in a flower-pot for about 

 twenty years, during which time it never appeared 

 above ground, but that at the end of the twenty years 

 it was as sound and fresh as when first put into the 

 pot. Its not appearing above ground was of course 

 due to its want of food supply, it being parasitic. 



Plants that have acquired the habit of parasitism — 

 whether partial or complete — may naturally be 

 expected to afford evidences of the time when they 

 lived free and independent lives, in the retention or 

 partial retention of organs or peculiarities of structure, 

 which were absolutely necessary for them in their free 

 and independent condition, but which are now of no 

 further service to them, the host performing the 

 function for the plant which its own structure enabled 

 it then to perform for itself. 



• The animal world affords numberless instances of 

 useless and aborted organs, evidently remnants of a 

 ■previous condition of existence requiring a different 

 organization ; and in the vegetable world, no doubt, 

 the instances will be found as numerous when the 

 same amount of attention has been given to it. We 

 already know of many modified leaves, aborted and 

 imperfectly developed styles, &c. &c., and as cur 

 knowledge of the physiology of plant-life increases, it 

 may reasonably be assumed that many remnants of a 

 past condition will be discovered. That they will be 

 so marked and diverse as in the animal world we 

 should not expect ; the functions and surroundings of 

 the one being so many and various in comparison with 

 those of the other. 



Z. squamaria affords us several remarkable and 

 interesting features, illustrating "adaptation to 

 environment " and the modification of organs to 

 perform functions other than those primarily per- 

 formed. 



The peculiar fleshy scales of the plant under con- 

 sideration I believe to be an excellent illustration of 

 the retention of organs no longer of service to the 



plant for their original function, and of the modifica- 

 tion of those organs, adapting them to the performance 

 of a new and totally different one. If a transverse 

 section be made of one of these scales, it will be found 

 to possess several irregularly-shaped cavities (Fig. 6), 

 and on the walls of these cavities will be found 

 numerous little gland-like bodies. 



These little bodies have been noticed by many 

 observers ; but what special function they perform 

 has not (so far as I can learn) been hitherto discovered. 

 In addition to these gland-like bodies, and scattered 

 between them on the surface of the cavities will be 

 seen numerous symmetrically arranged cells, reminding 

 one of stomata. What function, however, could 

 stomata possibly perform in this enclosed cavity ? 

 Certainly not the ordinary function of respiration. 

 But that they are stomata, although perhaps useless 

 and aborted, I think I have sufficient evidence to 

 prove. Also that the little gland-like bodies are 

 really glandular hairs, which, together with the 

 stomata, occupied their usual position on the inferior 

 side of the leaf of the plant before it acquired its 

 parasitic habit. 



How, why, and when Z. squamaria took upon itself 

 the habit of parasitism, are questions that can be 

 answered by speculation only. That the habit was 

 acquired gradually, we infer from observation — since 

 changes in habit, and still more in structure, can take 

 place but slowly. 



Probably the first act towards parasitism was the 

 developing of cells, which, coming into contact with 

 some other growing vegetable substance, had the 

 power of attaching themselves to it ; and as Z. 

 squamaria is a succulent, rapidly-growing plant, it 

 helped itself to the nutriment of its neighbour through 

 these attached cells. This habit gradually grew 

 until the plant became, as we now find it, wholly 

 dependent for its existence on some strong and 

 vigorous host. 



Probably this proclivity to parasitism was brought 

 about by the circumstances of its environment. What 

 these were we cannot know ; but that the habit 

 became necessary to its existence we may be sure, 

 and also that the cells possessing the function of 

 attachment and absorption must be considered as a 

 development or adaptation for this special function. 

 As the habit of parasitism developed, the leaves and 

 roots would gradually give up their own special 

 functions, and, if suitably positioned, would adapt 

 themselves to the new order of things ; the plant 

 either losing them entirely or partially, or modifying 

 them to new functions. Thus the leaves of Z. squa- 

 maria appear to have become modified. 



An examination of the very young scales will 

 reveal the fact, that they have apparently started 

 life as ordinary leaves ; instead, however, of develop- 

 ing a flat blade, as in an ordinary leaf, the young 

 leaf takes a sharp bend downwards, and folds back 

 upon itself, as in Fig. 7. The cells of the leaf 



