drop of resin on the bark, where a small insect had covered its dome-shaped body with a layer of resin, was as thin-walled as the shell of a mustard seed. In such a case we are called upon to suppose that a flow of resinous juices starts from below the insect, passes up over its body and nowhere else, and covers it with an even layer of resin. This is to me a difficult conception. On the other hand, it is easy to conceive how the insect simply feeding on the juices from below, and secreting this resinous substance from its body, could build such a shell of resin.

4. By careful examination of bark and wood, no puncture or abrasion could be detected at all adequate to account for such a spontaneous flow of the sap of the plant, as would produce the amount of resin present. This examination was repeated with the assistance of Prof. Joseph Le Conte, who concurred fully in the conclusion arrived at.

All these facts, so inexplicable on the exudation theory, appear to me to be readily explained on the basis of the insect origin of the gum. The insect fixes itself to a spot on the bark where it lives and dies. For its sustenance it is dependent on the sap of the plant. Certain plants are adapted to this purpose, others are not. The juices sucked up and absorbed by the insect serve as its food, and at the same time as material, from which is elaborated the resinous envelope, destined to serve as a protection for the eggs and larvæ. This resinous substance may be exuded from the entire surface of the insect, or from particular organs or glands; I am in no position to pursue this point, interesting as it is. This elaboration thickens as the insect grows older, and as the insects live in close proximity they become crowded and distorted, and the spaces between them compactly filled with their united elaborations, so that the result is as we see it, a resinous mass of coarse, irregular, cellular structure, with the egg-sac filling the cell, or, after the specimen is dried or the young escaped, with the shrunken remains of sac and eggs in the cell.

This explains the occurrence of practically the same resin on various plants-the form and structure of the resin-that it surrounds the sacs on all sides perfectly, but does not run off along the bark of the twig nor collect into solid drops or masses-a fact difficult to explain on the simple exudation theory. It also gives a definite meaning to the "alteration" of the juice by the insect referred to in "Chambers' Encyclopædia."

Whether the lac is to be considered as an excretion or secretion is very much a matter of definition. If by secretion we mean a definite substance elaborated by the organism for a definite purpose, this would appear to be a true secretion. On the other hand, once secreted it probably exerts no further internal function in the organism, and is in so far an excretion. In the same sense, hair, nails, epidermis, etc., continually discarded by the organism, might be considered excretions. However we may regard it, it is probably a normal product of the vital activity of the lac insect.

A somewhat striking objection against this theory is, that it is against analogy, that a well-marked resin should be the product of anímal life. But so also is the production of war by the bee against the same analogy, and yet it has been proven that bees confined to an exclusive diet of sugar will produce wax formed. by their own vital processes, and any philosophical distinction between wax and resin in this particular would, I think, be difficult to establish.

In conclusion, I would again reiterate that I am by no means certain that the question of the origin of the lac has not been settled by observers more directly interested in natural history, but if so, our chemists and encyclopædists have been slow to find out the facts, and our most recent authorities, with few exceptions, adhere to the exudation theory. If this communication has the effect of bringing to notice previous work, or gives rise to more complete investigations in the future, it will be as much as I can expect from it.

IN

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BOTANIZING ON THE COLORADO DESERT.

BY EDWARD LEE GREENE.

I.

'N February of 1877, by way of the stage road between San Diego and Fort Yuma, I made a little expedition across the interesting region above named. A desert is not naturally supposed to be the most eligible locality, nor midwinter the best season for making botanical excursions, yet seldom has a week's recreation of that kind given me more satisfaction than that upon which I have preserved the following notes:

In passing from west to east across Southern California, the

first glimpse one gets of the desert is a fine bird's-eye view. From the San Diego plains, all treeless, brown and dusty, an easy two days' journey brings the traveler up to the level of that broad plateau which constitutes the summit of the coast range. Across this forty-five miles of mountain top, one travels pleasantly; now through handsome groves of evergreen oaks, then among a succession of low, rounded, stony hills, between which some bits of fresh, green mountain pasture spread themselves; here passing a settler's cabin with its newly ploughed fields and its group of blooming peach trees, and there meeting a merry, boisterous gang of mountain herdsmen. Having thus come to the eastern verge of the plateau, the great wilderness breaks all at once upon the view, beginning a dizzy half mile down beneath your feet, and stretching away to the eastward for a hundred miles. It was past the middle of the afternoon when I reached this interesting point, and paused to rest a while and to enjoy the novel scene, so desolately grand, which lay before me. The region in question is far from being a flat monotonous expanse of naked sands.

Its general level is broken by many abruptly rising knobs and peaks and by several prolonged chains of high and sharply defined rocky hills, all lifting themselves up like precipitous islands above the even surface of a sea; and although these peaks and ranges are destitute of verdure, and red as the sands that drift about their bases, they yet combine to make a most impressive picture when viewed at a distance, and from this aerial elevation where the desert first appears in sight. Aware that the stage station where I must pass the night was not more than two miles away by the steep, winding road, I lingered here until the sun was near his setting, and the shadows of the peaks and pyramids I sat among, were measuring their dark lengths upon the plain afar below, and the purple evening clouds had reflected their own almost gorgeous coloring to the vast, varied landscape that stretched eastward and northward so very far away. This strange sunset scene was beautiful beyond all description, and will be treasured for a lifetime in the beholder's memory.

Having descended from these picturesque heights, it was nearly dark when, as the road led around a sharp angle of the mountain, I found myself almost at the door of the stage company's little hotel. Here were pleasant sounds; the music of water trickling

down through an iron pipe from a small spring that rises among rocks which almost overhang the house hundreds of feet above; and by the way, the sound of running water is never so musical as when one has traveled six hours in torrid heat without having tasted a drop. Music also of insects was here, evidently some sort of bees which, even in the late twilight, were humming amid the rosy, flower-laden boughs of the desert almond. This handsome bush (Prunus andersonii Gray), when in flower, resembling a small peach tree, contrasts very prettily with its associates, the cacti and agaves which thrust forth their clumsy, graceless forms from every niche and crevice of this grand mass of rock which walls in the desert on the west. While most trees and bushes of that genus require good soil and a fair supply of moisture, this species appears to thrive, like the spiny cacti, on nothing more substantial than the sunburnt rocks and the desert air.

The condition in which I found the solitary tenant of this isolated hostelry illustrates one of many dangers to which the lone keepers of these desert stations are exposed. He was bending over a basin of water bathing his head and face, which parts, as I could see by what remained of daylight, were bleeding freely. He seemed in too much pain to notice the near approach of the stranger, at whose unexpected presence the man's sole household companion, a fierce bull-dog, tugged away at the end of the chain in a rage which I should not have smiled at had the chain been a light one. Presently, however, the man tied a bandage about his head, unbent himself, turned toward the door where I was standing, and I inquired what had befallen him. He replied that he had, a few moments previous to my coming, gathered himself up from the stable floor where he had been lying unconscious he hardly knew how long, having been kicked by a vicious stage horse left in his keeping. Luckily for him and somewhat so for me, tired and hungry as I was, the wound was not serious. He was an intelligent youth, intelligent enough to comprehend my reason for undertaking a walk across the desert. Under his cabin roof I fared well, and on the hardest of beds enjoyed such sound, refreshing sleep as is given to tired but happy travelers.

From this hostelry among the cliffs, a few minutes' morning walk brought me to where the mountain flanks are parted by a deep gorge indicating where, in times long past, a river made its way from the highlands down to the sea which then occupied the

dry bed of

The grade

area now a desert. The road here descends to the the extinct river, and follows it directly to the plain. is easy but the loose white sand is deep, and in this sandy rockwalled passage I met two Indians, a man and woman, whose decrepid forms, withered features and whitened hair made them look almost prehistoric, toiling upward on foot, each with a heavy pack of blankets and pottery on their backs, while a few rods behind them a stalwart youth of about thirty years rode in serenest laziness a half-starved looking pony. It was probably another party of herborizers this, on their way up to the rocky heights where the wild maguey plants grow, to feast on the tenderly springing flower-stalks, and make mezcal.

February days in this region are nearly as warm as days of July in New England, and as I walked along the south wall of the cañon, gratefully sheltered from the heat of the morning sun, I easily comprehended the origin of that oriental phrase: “The shadow of a great rock in a weary land." Here at my feet, where the sand was shaded, grew and bloomed a low spreading variety of evening primrose (Enothera), with large, pale yellow flowers. On the opposite side, more exposed to the sun, the whole base line of the rising cliffs was ornamented with a continuous hedgerow of a very handsome shrub (Hyptis albida H. B. K.) with whitish foliage, its branchlets ending in slender spikes of fine, deep purple flowers. The desert shrubs, however brilliant their flowers may be, are usually without much show of foliage, most of them bearing spines or briers instead of leaves.

But besides this pretty, white-leaved Hyptis, I noticed one other exception to that rule in the case of a smaller bush (Beloperone californica Gray), the stems of which were buried half their length in the drifting sands, and whose salvia-like spikes of scarlet flowers were subtended by neat foliage of a bright shining green. From admiring these first beauties of the desert, my attention was next drawn to a tuft of tall, slender, reed-like stems with pale-green bark which, though appearing wholly leafless, produced at their summits several pendant clusters of white flowers. At a few rods distance one would never have guessed this graceful plant to be a near relative of the stout coarse leaved silk-weed of Eastern fields and waysides; but a glance at the structure of the flower showed the plant to be a genuine Asclepias (A. subulata Dec.). The stems, though altogether smooth