March 3, 1893.] 



SCIENCE. 



117 



to form pockets capable of holding water, and that if these pock- 

 ets are filled with water the trichomes. both outside and inside, 

 will be submerged. 



Also in Tulips the tightly-folded sheathing base is covered on 

 the inside with a large number of thin-walled hair-like trichomes. 

 In fact, the resemblance to root-hairs was quite close. The leaf 

 was adapted for guiding any water that might fall upon it di- 

 rectly to this region of trichomes. Here it seems possible, as also 

 in the Bilbergias, that the plants may have developed, becaupe of 

 a change in the conditions under which they grow, these addi- 

 tional absorbing structures. 



A series of experiments, however, failed to give conclusive 

 praof of this function. Several innocuous liquid stains were 

 placed and retained for hours, and even days, in these axillary 

 pickets, after which sections were made of various parts of the 

 stem. In a few instances the tissues were unmistakably stained. 

 Oftener, however, no trace of absorbed stain could be found. 



Yucca, a plant of arid regions, possibly also absorbs water 

 through the base of the petiole, since we find on that part of the 

 petiole which is wholly buried among the petioles of the sur- 

 rounding leaves a large number of stomata. 



These stomata may absorb water trickling into this region 

 without at other times subjecting the plant to dessication, as they 

 would if found on exposi d parts of the leaf. 



Now as to the root-hair area. Do we find in these plants whose 

 leaves direct the water toward the main axis that the area of 

 root-hairs is near the axis, and, on the other hand, that where the 

 water is drained outward it will fall near the region of greatest 

 root activity? 



I believe we do in a very large majority of cases. There are 

 plenty of exceptions, but I believe they are exceptions and not 

 the rule As examples note all the grasses with fibrous roots, 

 and many other Endogens growing from corms, bulbs, and 

 rhizomes, from which grow out great masses of short, fibrous 

 roots. On the other hand, note the forest trees, generally shed- 

 ding the water outward and carrying the water toward if not to 

 the root-hair area. But now I am not going to assert that the 

 groove has been developed in order to direct the water inward, 

 nor that the branches droop in order to carry it outward. On the 

 contrary, if the root-hair areas are found as I have asserted, it is 

 because these are the areas of greatest moisture, not that these 

 have been made the areas of greatest moisture because the root- 

 hairs existed there. The plant in sending out its roots seeks for 

 moisture, and where that moisture and food is found in its most 

 available form, it will develop root-hairs. 



It does not seem then that the position of the root-hair area 

 had any thing to do with the original formation of a grooved 

 petiole, and I will again stale that I believe the grooved petiole 

 co-existent with anl a necessity to the endogeneous type of vege- 

 tation. 



THE CLEANSING FUNCTION OF HAIRS. 



BY HENBT SEWELL, PH.D., MD , DENVER, COLO 



The student of animal morphology is never so happy as in the 

 ijiscovery of a rudimentary organ or some structure which seems 

 a worthless burden to its possessor; for, with an unacknowledged 

 belief in a sort of teleology, he hopes by finding the origin of the 

 useless appendage that the tangle of phylogeny may be loosened. 



The student of animal physiology, on the other hand, is never 

 more complacent than when to an apparently useless structure rr 

 unmeaning arrangement he can attribute some function by 

 virtue of which the body is made a more eflicient machine. 



An interesting example of the subservience of form to function, 

 which the writer has never seen mentioned, is found in the ar- 

 rangement of the epidermic scales which form the outermost 

 layer of animal hairs. The buried edges of the scales point 

 towards the root of the hair, while the free edges project obliquely 

 in the direction of the hair end, as the shingles on a roof pomt 

 to the eaves. When a hair is drawn between the thumb and 

 forefinger, which are gently pressed upon it, it will he found 

 that the hair glides far more easily when pulled from root to tip 



than in the opposite direction. "When the hair is simply rolled 

 between the thumb and finger it will gradually move parallel to 

 its length in the direction of the hair root. These results depend 

 altogether on the way in which the hair-scales project from the 

 hair axis. It is at once obvious that foreign particles clinging to 

 the hair in situ would find easy the passage outward towards the 

 tip and away from the surface of the body, but exceedmgly diffi- 

 cult the progress in the opposite direction. Every movemtntof 

 the hair, especially frictional disturbance, must set up a current 

 of foreign particles towards the hair tip. The housewife has 

 long known by experience how much more readily a vigorous 

 shaking cleanses a v\oolen garment than one made of cotton. 



The sebaceous glands opening at the mouth of the hair follicle, 

 probably play an important part in surface cleansing; for their 

 oily secretion sticks together the particles of shed epithelium, 

 associated with all manner of filth, in such a manner that the 

 "hair-rakes" can, no doubt, more easily remove them. 



Ludwig long ago showed that, in the same way, the mucus 

 secreted by the surface epithelium of the stomach and intestines 

 agglutinates the detritus which covers the mucous membrane 

 after digestion, and so makes possible its removal by the peris- 

 taltic action. The housewife, again, uses the same principle 

 when she sprinkles a very dusty floor before sweeping, and finds 

 the filth to roll before her broom. 



One mere reference to physiological body-cleaning: It has 

 been found that the growth of epidermic epithelium proceeds in 

 such a way, at least in certain situations, as to remove the worn- 

 out cells en masse. Thus, on the external surface of the ear- 

 drum, the direction of growth is such that the epithelial scales 

 progress, pushed from below, steadily from the centre of the 

 membrane and then along the meatus to the exterior. Foreign 

 panicles lying on the epidermis are of course carried with it. 



NOTES AND NEWS. 



The first annual meeting of the Ohio Academy of Science was 

 held at Columbus on Dec. 29-30. 1893. After some formal busi- 

 ness, such as the appointment of committees, had been attended 

 to, the reading of papers began. The following, among others, 

 were read during the session: The Advantages of Arzama obli- 

 qiiata for Laboratory Instruction, D. S. Kellicott; The Inhabitants 

 of a Species of Gall on Wheat Hants, F. M. Webster; Some Anti- 

 clines found in the Shales of Northeastern Ohio, Geo. H. Colton; 

 Lantern Slides without a Negative, W. G. Tight; A Few Rare 

 Ohio Plants, Aug. D. Selb.v ; New Plants for the Flora of Ohio, 

 W. 0, Werner ; Notes on the Distribution of Some Rare Plants in 

 Ohio, W. C. Werner; Lichens of Ohio, E E Bogue; Leaf Varia- 

 tion : Its Extent and Significance, Mrs W. A. Kellerman; Some 

 Insect Migrants in Ohio, F. M. Webster; The Uredine® of Ohio, 

 Freda Detmers; Ohio Erysiphese, Aug. D. Selby; The Develop- 

 ment of the Berea Stone Industry, J. H. Smith; ^now-Rollers, 

 W. S. Ford ; Note on a Nest of White Ants, O. L. Sadler and 

 Mrs. O. L, Sadler; The Histology of the Stem of Pontederia cor- 

 data L,, E. M. Wilcox; Pulmonary Fistula in a Frog, J. B. 

 Wright; Note on a Skull Pierced by a Stone Spear-Head, E. W. 

 Claypole. In the evening the president, Dr. E. W. Claypole, de- 

 livered the annual address, taking for his subject "Devonian 

 Ohio, or a Passage in the Making of the State." Premising that 

 such an address should not be one intelligible only to geologists, 

 as the majority were not specially devoted to that science, he 

 outlined the geological history and growth of the region from 

 the commencement of the deposition of the Corniferous Limestone 

 to the base of the Berea Grit. The first part of the era was a time 

 of profound peace, when a coral sea overlay all the State. This 

 was followed by a time of depression, when the vast beds of shale 

 were laid down. The fishes of that era, as preserved in these 

 shales, came in for full consideration, and their immense tony 

 plates were illustrated by numerous drawings. The leading gen- 

 era were Titanichthys, Dinicbthys, and Gorgonichthys. Mr. W. 

 K. Moorehead was appointed a committee on archeology, es- 

 pecially with a view to the investigation of the antiquities of 

 Ohio, and Professor G. F. Wright was made a committee on 

 boulders. 



