708 



SCIENCE. 



[Vol. II., No. 43. 



as to its source. The report was, " It seems 

 to be mo stlj- calcium oxalate, with some carbo- 

 nate and organic matter." The crystals per- 

 tain to the mouocliuic system, like the mineral 

 whewellite. In another decayed white oak ex- 

 amined, the pulverulent liber, of darker appear- 

 ance than in the former, consisted of crystals, 

 cellular cUbris, with no bast-fibres, but with 

 numerous long, dark-brown, many-celled spo- 

 ridia of a fungus, and a few dead rotifers. 

 Under similar circumstances, the same kind of 

 crystals, equall}' abundant, were observed in a 

 dead chestnut- tree. 



The liber of the fresh or undecayed white 

 oak and chestnut exhibits the calcium-oxalate 

 crystals arranged in close longitudinal rows, as 

 represented in fig. 3, situ- 

 ated among the bast-fibres, 

 and nearh" as abundant. 

 The crystals are smaller, 

 approaching the ends of 

 the series ; and the spaces 

 occupied bj- the latter taper 

 at the extremities. Each 

 ci-ystal occupies a separate 

 cuboidal cell, or at least 

 a distinct compartment of a 

 long fusiform space, bound- 

 ed by the bast-cells. In 

 the rows of crystals of the 

 white oak, from twenty-five 

 to thirty-five were counted, 

 occupying a space of about 

 the fiftieth of an inch in 

 length. In the chestnut 

 liber, from twenty-five to 

 forty - five crj'stals were 

 counted in different rows. 

 In the liber of the butter- 

 nut the crystals are com- 

 pounded in spheroidal clusters, and form rows 

 arranged in the same manner as in the pre- 

 ceding trees. 



Without having had anj- intention of inves- 

 tigating the occurreuce of crystals in plants, I 

 have been led to make the present communica- 

 tion on what, to botanists, maj' be a familiar 

 fact, under the impression that manj', like mj'- 

 self, have heretofore been ignorant of it ; and 

 this for the reason that sufficient notice of the 

 matter h as not been given . Our ordinary manu- 

 als, while referring to the occurrence of crj's- 

 tals in plants, and giving a few illustrations 

 of those observed in herbaceous plants, take 

 almost no notice of the beautiful forms in the 

 inner bark of our forest-trees. The ' Micro- 

 graphic dictionary ' mentions the occurrence 

 of raphides in the bark and pith of many 



Fig. 1. — Calcium-oxa- 

 late crystal. 



Fig- 2. — Twin form of 

 the same. Both from 

 decayed liber of the 

 ■white oak, magnified 

 250 diameters. 



Fig. 3. — Portion of a 

 series of crystals from 

 fresh liber, magnified 

 300 diameters. 



woodj- plants, as the lime and vine, but makes 

 no reference to, nor gives illustrations of, such 

 as occur in oaks, the chestnut, the hickory, etc. 

 Xo more beautiful example of plant-crystals 

 can be so readily obtained than that exhibited 

 in thin slips of the liber of the oak or chest- 

 nut. 



Although the occurrence of crystals in vege- 

 table tissues was observed and described b}' 

 Payen in 1841 {Comjites rendus de Vacadi- 

 mie des sciences), the first and fullest account 

 of the crystals of the liber of forest and fruit 

 trees was given by Prof. J. W. Bailey, in a 

 communication to the American association of 

 geologists and naturalists, in 1843, afterwards 

 pubhshed, with a plate, in the American jour- 

 nal of science for 1845, p. 17. Sanio subse- 

 quently described the same crystals in the 

 Monatsberichte of the Prussian academy of 

 sciences for 1857. Joseph Leidy. 



THE PHYSIOLOGICAL STATION OF 

 PARISH — 11. 



The blacli screen shown in fig. 4 is a kind of shed, 

 three metres in depth, fifteen long, and four high. 

 This height is necessary in photographing birds on 

 tlie wing; for, on rising, they immediately leave the 

 dark field. ^Alien the walk of a man or an animal Is 

 being studied, the opening of the screen is limited by 

 a frame covered with black cloth suspended from 

 its upper part : this regulates the ingress of light 

 under the shed, and makes its cavity darker. In ad- 

 dition, a long strip of velvet two metres and a half 

 broad fills all the lower part of this cavity. Thus the 

 light coming through the bottom of the screen is al- 

 most entirely cut off. 



In fig. 4 a man dressed entirely in white is walking 

 .before the dark screen. The course on which he 

 walks is slightly inclined, in such a way that a visual 

 ray, proceeding from the objective, passes very near 

 the surface of the ground without tneeting it anywhere. 

 This is necessary in order that in the picture the feet 

 of the walker may be entirely visible, while the ground 

 is not : otherwise the light reflected from the ground 

 would make an imjjression on the sensitive plate at 

 the very jjoints where the images of the feet should be 

 produced, and make them obscure. The course is 

 raised about twenty centimetres above the sun-ound- 

 ing ground; and along the full length of this relief 

 there runs a plank on which alternate divisions, each 

 a metre and a half long, are painted black and 

 white. The plank thus divided is seen in the photo- 

 graphs, and is useful in measuring the distance run 

 between two successive images, and in estimating 

 the size of the subject, the amplitude of his reactions, 

 and the extent of displacement of each part of his 

 body. In order to know the rapidity of movement, 

 the time consumed in traversing the various spaces 

 must be measured. Now, if the machinery which 

 ^ Concluded from No. 42. 



