Page:Popular Science Monthly Volume 7.djvu/143

Rh perform functions, by which they are allied to all other plants and closely related to one of the largest groups of the vegetal kingdom. They stand, in fact, at the head of the class of fungi, of which there are at least as many species as of all flowering plants put together.

These singular forms, though low in the scale when compared with the green and blossoming world around us, are yet complex and imposing when contrasted with the world of plant-life revealed by the microscope. They have a distinct vegetative system, and a highly-organized reproductive system. On examining the common cultivated mushroom, a species which grows wild in meadows and pastures, these separate systems may be readily distinguished. The vegetable mould or decaying substance on which it grows is penetrated with grayish-white delicate interlacing filaments which are represented by the root-like fibres shown in Fig. 1. This webby mass constitutes the vegetative portion of the plant. It is called the mycelium, or, among dealers, the spawn, as by its means the plant is propagated in cultivation. In a dry state it may be kept dormant for a long time, and wall grow into a perfect plant under the influence of heat, moisture, and other favoring conditions.

From this mycelium arises the reproductive system—that portion of the mushroom which is seen above-ground and which may be compared to the inflorescence of higher plants. It consists of the long thick stem or stipe and the umbrella-like top, called the cap or pileus. On the lower surface of this cap vertical plates are seen radiating from the stem, though not connected with it. These plates are known as gills, and in a living specimen they will be found covered on all sides by a delicate membrane called the hymenium. Upon this hymenium are borne the reproductive bodies or spores, which are analogous to seeds.



To make our conception of the structure of this mushroom more complete, we will trace its growth from the beginning. The first visible portion is the mycelium, at certain points of which there appear, at an early stage, round tubercles not larger than a mustard-seed, which rapidly increase in size, push through the soil, and become more or less elongated, resembling the shaded cut in Fig. 2. There is yet no external sign of cap or gills, but a section of the tubercle will reveal