Sept. 3, 1874] 



NATURE 



369 



this is only found at the upper part of the tube. Bartram must 

 be credited with the suggestion, which lie, however, only put 

 forward doubtfully, that the insects were dissolved in the fluid, 

 and then became available for the alimentation of the plants. 



Sir J. E. Smith, who published a figure and description of 

 Sarraceiiia variolaris, noticed that it secreted fluid, but was con- 

 tent to suppose that it was merely the gaseous products of the de- 

 composition of insects that subserved the processes of vegetation. 

 In 1829, however, thirty years after Bartram's book, Burnett 

 wrote a paper containing a good many original ideas expressed 

 in a somewhat quaint fashion, in which he very strongly insisted 

 on the existence of a true digestive process in the case of Sarra- 

 cenia, analogous to that which takes place m the stomach of an 

 animal. 



Our knowledge of the habits of Sarracenia variolaris is now 

 pretty complete, owing to the observations of two South Carolina 

 physicians. One, Dr. M'Biide, made his observations half a 

 century ago, but they had, till quite recently, completely fallen 

 into oblivion. Me devoted himself to the task of ascertaining 

 why it was that Surmciiiia -I'drioiaris was visited by flies, and 

 how it was that it captured them. This is what he ascertained : — 



" The cause which attracts flies is evidently a viscid substance 

 resembling honey, secreted by or exuding from the internal sur- 

 face of the tube. From the m.Trgin, where it commences, it 

 does not extend lower than one-fourth of an inch. The falling 

 of the insect as soon as it enters the lube is wholly attributable 

 to the downwaid or inverted position of the hairs of the internal 

 surface of the leaf. At the bottom of a tube split open, the 

 hairs are plainly discernible, pointing downwards ; as the eye 

 ranges upward they gradually become shorter and attenuated, 

 till at or just below the surface covered by the bait they are no 

 longer perceptible to the naked eye, nor to the most delicate 

 touch. It is here that the fly cannot take a hold sufficiently 

 strong to support itself, but falls." 



Dr. Mellichamp, who is now resident in the district in which 

 Dr. M 'Bride made his observations, has added a good many par- 

 ticulars to our knowledge. lie first investigated the fluid which 

 is secreted at the bottom of the tubes. He satisfied himself that 

 it was really secreted, and describes it as mucilaginous, but leav- 

 ing in the mouth a peculiar astringency. He compared the 

 action of this fluid with that of distilled water on pieces of fresh 

 venison, and found that after fifteen hours the fluid had produced 

 most change, and also most smell ; he therefore concluded that 

 as the leaves when stuffed with insects become most disgusting 

 in odour, we have to do, not with a true digestion, but with an 

 acceleiated decomposition. Although he did not attribute any 

 true digestive power to the fluid secreted by the pitchers, he 

 found that it had a remarkable anesthetic effect upon flies im- 

 mersed in it. He remarked that " a fly when thrown into water 

 is very apt to escape, as the fluid seems to nin from its wings," 

 but it never escaped from the Sarracenia secretion. About half 

 a minute after being thrown in, the fly became to all appearance 

 dead, though, if removed, it gradually reco\ered in from half an 

 hour to an hour. 



According to Dr. Mellichamp, the sugary lure discovered by 

 Dr. M 'Bride, at the mouth of the pitchers, is not found on either 

 the young ones of one season or the older ones of the previous 

 year. He found, however, that about May it could be detected 

 without difficulty, and more wonderful still, that there is a honey- 

 baited pathway leading directly from the ground to the mouth, 

 along the broad w ing of the pitcher, up which insects are led to 

 their destruction. From these narratives it is evident that there 

 are two very different types of pitcher in Sarracenia, and an 

 examination of the species shows that there may probably be 

 three. These may be primarily classified into those with the 

 mouth open and lid erect, and which consequently leceive the 

 rain-water in more or less abundance ; and those with the mouth 

 closed by the lid, into which rain can hardly, if at all, find 

 ingress. 



To the first of these belongs the well-known S.purpntca, with 

 inclined pitchers, and a lid so disposed as to direct all the rain that 

 falls upon it also into the pitcher ; also S.Jlara, rubra, and Drum- 

 monaii, all with erect pitchers and vertical lids ; of these three, 

 the lid in a young state arches over the mouth, and in an old 

 st.ate stands nearly erect, and has the sides so reflected that the 

 rain which falls on its upper surface is guided down the outside 

 of the back of the pitcher, as if to prevent the flooding of the 

 latter. 



To the second group belong S. psiltacina and S. variolaris. 



The tissues of the internal surfaces of the pitchers are singu- 

 larly beautiful. They have been described in one species only, 



the S. purpurea, by August Vogl ; but from this all the other 

 species which I have examined differ materially. Beginning from 

 the upper part of the pitcher, there are four surfaces, charac- 

 terised by difierent tissues, which I shall name and define as 

 follows :— 



1. An (7///af//OT surface, occupying the inner surface of the 

 lid, which is covered with an epidermis, stomata, and (in 

 common with the mouth of the pitcher) with minute honey- 

 secreting glands ; it is further often more highly coloured than 

 any other part of the pitcher, in order to attract insects to the 

 honey. 



2. A conducting surface, which is opaque, formed of glassy 

 cells, which are produced into deflexed, short, conical, spinous 

 processes. These processes, overlapping like the tUes of a house, 

 form a surface down which an insect slips, and. affords no foot- 

 hold to an insect attempting to crawl up again. 



3. A glandular surface (seen in S. purpurea), which occupies 

 a considerable portion of the cavity of the pitcher below the 

 conducting surface. It is formed of a layer of epidermis with 

 sinuous cells, and is studded with glands ; and being smooth 

 and polished, this too affords no foothold for escaping insects. 



4. A delcntivc surface, which occupies the lower part of the 

 pitcher, in some cases for ncaily its whole length. It possesses 

 no cuticle, and is studded with deflexed, rigid, glass-hke, needle- 

 foimed, striated haiis, which further converge towards the axis of 

 the diminishing cavity ; so that an insect, if once .amongst them, 

 is effectually detained, and its struggles have no other result than 

 to wedge it lower and more firmly in the pitcher. 



Now, it is a very curious thing that in .S. purpurea, which has 

 an open pitcher, so formed as to receive and retain a maximum 

 of rain, no honey-secretion has hitherto been found, nor has any 

 water been seen to be secreted in the pitcher ; it is, further, the 

 only species in which (as stated above) I have found a special 

 glandular surface, and in which no glands occur on the detentive 

 surface. This concurrence of circumstances suggests the possi- 

 bility of this plant either having no proper secretion of its own, 

 or only giving it off after the pitcher has been filled with rain- 

 water. 



In .S'. /lava, which has open-mouthed pitchers and no special 

 glandular surface, I find glands in the upper portion of the deten- 

 tive surface, among the hairs, but not in the middle or lower part 

 of the same surface. It is proved that S.Jlava secretes fluid, but 

 under what jirecise conditions I am not aware. I have found 

 none but what may have been accidentally introduced in the few 

 cultivated specimens which I have examined, either in the full- 

 grown state, or in the half-grown when the lid arches over the 

 pitcher. I find the honey in these as described by the American 

 observers, and honey-secreting glands on the edge of the wing 

 of the pitcher, together with similar glands on the outer surface of 

 the pitcher, as seen by Vogl in .S'. purpuj ea\ a 



Of the pitchers with closed mouths, I have examined those of 

 S. t'ariolaris only, who^c tissues closely resemble those of .S./f^r'^r, 

 That it secretes a fluid noxious to insects there is no doubt, 

 though in the specimens I examined I found none. 



There is thus obviously much still to be learned with regard 

 to Sarracenia, and I hope that American botanists will apply 

 themselves to this task. It is not probable that three pitchers, 

 so differently constructed as those of S. Jlava, purpurea, and 

 variolaris, and presenting such differences in their tissues, should 

 act similarly. The fact that insects normally decompose in the 

 fluid of all, would suggest the probability that they all feed on 

 the products of decomposition ; but as yet we are absolutely 

 ignorant whether the glands within the pitchers are secretive, or 

 absorptive, or both ; if secretive, whether they secrete water or 

 a solvent ; and if absorptive, whether they absorb animal matter 

 or the products of decomposition. 



It is quite likely, that just as the saccharine exudation only 

 makes its appearance during one particular period in the life of 

 the pitcher, so the digestive functions may also be only of short 

 duration. We should be prepared for this from the case of the 

 Diona;a, the leaves of which cease after a time to be fit for 

 absorption, and become less sensitive. It is quite certain that 

 the insects which go on accumulating in the pitchers of 

 Sarracenias must be far in excess of its needs for any legitimate 

 process of digestion. They decompose ; and various insects, too 

 wary to be entrapped themselves, seem habitually to drop their 

 eggs into the open mouth of the pitchers, to take advantage of the 

 accumulation of food. The old pitchers are consequently found 

 to contain living larva: and maggots, a sufficient proof that the 

 original properties of the fluid which they secreted must have 

 become exhausted ; and Barton tells us that various insectivorous 



