34 THE AMERICAN MONTHLY [Fel.rnary, 



completeness. It contains one preparation each of vegetable and ani- 

 mal anatomy. The vegetable section is a transverse one of the stem of 

 maize, selected as presenting a typical Monocotyledon, is mounted in 

 balsam, and is to be viewed with polariscope and paraboloid. Roots 

 in general are first described. Beyond their primary function of fixing 

 plants to the ground and absorbing nutriment therefrom, roots are often 

 reservoirs of nutritious matter and become greatly enlarged, e. o-., the 

 turnip, carrot, etc. Aerial roots formed by tree ferns and orchids are 

 modifications meeting special needs : in orchids both fibrous and bul- 

 bous roots are devoloped. the one as organs of absorption, and the otlier 

 storing up nutriment. The microscopic characteristics of root are then 

 described. The "stem of a plant is the organ which develops leaves, 

 flowers and fruits ; the part of the plant which grows in an opposite 

 direction from the roots, shooting upwards through and above the 

 ground. The popular application of the term " stem " to that portion 

 only which grows above the earth is incorrect, for manv plants possess 

 under-ground stems. For further descriptions of stems, the student is 

 refered to text-books of botany. The forms o^stems are then consid- 

 ered, the tvpical form, approaching the cylindrical, and its variations. 

 The special functions of the stem are the support of the leaves, flowers, 

 and fruits, and the conveyance, through channels, throughout the plant 

 of the nutritious compounds absorbed from the soil. The nature and 

 texture of stems vary according to the duration of the life of plants ; 

 annuals, and biennials having as a ride soft stems, while perennials and 

 trees have stems more or less woody. 



Numerous bundles of fibro-vascular tissue are scattered throughout tlic 

 stems of monocotyledonous plants, the whole structure being invested 

 with an epidermis. A plate represents an isolated fibro-vascular bun- 

 dle, surrounded by the ground tissue of the stem. The two large ovoid 

 orifices lying side by side in the centre of the fibro-vascular bundle are 

 very wide vessels, having pitted markings and comparatively thin walls. 

 The circular orifice between these is a spiral vessel : the oval space 

 under this is a vessel with annular markings or thickenings, and below 

 it is an air space. Between the two large central vessels lie tracheides^ 

 which convev water. Above and between the pair of central vessels is 

 a patch of soft bast formed of sieve tubes, whose function is the con- 

 veyance throughout the plant body of nitrogenous food supplies. A 

 sheath of narrow, elongated, thick-walled cells {^sclercnchvma^ com- 

 pletelv surrounds and protects each fibro-vascular Innidle. Ifatran- 

 verse section of stem of maize be examined, there will be seen — 



1st. The epidermis^ formed of flattened cells (protected liy a cuti- 

 cle) , with openings {stottzata) here and there through it. 



2d. A layer of cells with thick walls {sclcrcnc/ivfua) developed in 

 order to strengthen the stem. 



3d. The ground tissue, made up of tliiu-walled ptrciichvmatous 

 cells, with inter-cellular spaces. 



4th. The Jihro-vasc7ilar bundles, distriluitcil through, and sur- 

 rounded bv, the ground tissue, as already describctl. 



The remaining slide of this box is a section of normal human kidney, 

 hardened in Midler's fluid and spirit, cut with the freezing microtome, 

 stained with logwood and eosine, and mounted in Canada balsam, and it 

 is described with the minuteness, completeness, and lucidity of tlie first 

 preparation. 



