50 SEEDS AND SEEDLINGS. 



is nothing except the young plant, are called non-endospermic, 

 e.g. Beans, Peas, Acorn. See Art. 83. 



* 81. Further Work with Seeds and Seedlings should be carried 

 out as time permits. Soak, dissect (remove coat, cut sections), and 

 examine with lens as many different seeds as possible. Test cut sur- 

 faces with (1) iodine solution for starch (blue) and proteids (brown) ; 

 (2) a drop of strong sugar solution, followed by a drop of strong sul- 

 phuric acid (bright red colour = proteids) ; (3) nitric acid and ammonia 

 (yellow colour = proteids). Practically all seeds contain proteids, 

 together with starch or oils. If the seed gives only a brown colour 

 with iodine, showing the absence of starch, try the tests for oil (Art. 69), 

 and for cellulose (Art. 86). Cut thin sections and examine them with 

 the microscope. In Maize and Wheat note the outermost layer of 

 cubical cells in the endosperm, packed with proteid grains ("aleurone- 

 grains "), also the layer of columnar cells (epithelium-layer) on the 

 surface of the cotyledon, which secretes ferments. 



Sow the seeds in moist sawdust or soil, note the temperature required 

 (or most favourable) for germination in each case ; examine and sketch 

 the seedlings from time to time. In moistened seeds of Linseed, 

 Cress, Turnip, Mustard, notice the jelly formed by the swelling of the 

 gummy seed-coat when it absorbs water. Small seeds e.g. Cress, 

 Wheat should be grown on muslin or flannel stretched over a tumbler 

 filled with water ; examine the roots for root-hairs and rootlets. 



* 82. Seeds with Food stored in Youngf Plant. Examine the seeds 

 and seedlings of Linseed, Cress, Mustard, Turnip, Radish, "Garden 

 Nasturtium" (Tropaeolum), Horse Chestnut, Vegetable Marrow, Melon. 



In nearly all cases the cotyledons are carried up into the air by the 

 lengthening of the hypocotyl. In Horse Chestnut the large cotyledons 

 are partly fused together ; notice that on germination the young stem 

 and root are pushed out of the seed by the lengthening of the cotyle- 

 don stalks. In Vegetable Marrow and Melon notice the method by 

 which the seedling gets its cotyledons out of the cavity enclosed by the 

 rigid walls of the flat seed ; an outgrowth (" peg") is formed to hold 

 down the lower half of the seed-coat against the soil, while the growing 

 shoot raises the upper half of the seed-coat and thus gets free. 



In Mustard the cotyledons are two-lobed, in Cress (Fig. 13) they 

 are three-lobed. In the " Nasturtium " (Tropaeolnm majiis) the later 

 leaves have a nearly circular blade with even margin, and the stalk 

 is inserted at the centre of the lower side of the blade, but in the ear- 

 liest leaves of the seedling the leaf-blade is lobed and the stalk in- 

 serted at the lower margin, as in the adult leaves of the closely-allied 

 leaves of the Canary Creeper (T. canariense). In Brazil " nut" (really 

 a seed) the hard shell is the seed-coat ; the minute cotyledons occupy 

 the broader end of the embryo, the root being at the narrow end. The 

 greater part of the embryo consists of the swollen axis (hypocotyl), 

 whose cells contain proteid and oil. The two cotyledons and the 

 plumule can be seen in a section examined with the microscope if the 

 section has been cut in exactly the right place. 



