ORCHIDS 299 



is said to be "inferior." The nearly related Iris has its 

 sepals reflexed and its petals erect: its stamens are three, 

 and the three style branches are broad and spreading. 

 The ovary is inferior as in Amaryllis. 



545. Orchids (Orchidales). Here the ovary is in- 

 ferior as in Amaryllis, but the 

 perianth is made up of imequal 

 and unlike segments, the stamens 

 are reduced to two or one (very 

 rarely three), and the tricarpel- 

 lary pistil has but two functional 

 stigmas in the large majority of ^'°- ■'dfil^nd o^otof"^*'^ 

 species. 



546. In all the foregoing Monocotyledons the embrj^os 

 have one cotyledon, the stems have scattered vascular 

 bundles, the leaves are alternate on the stems, and paral- 

 lel-veined, and the perianth whorls are ternate. 



Laboratory Studies. Note: In these studies, and those 

 upon Dicotyledons, the aim should be to bring out the succes- 

 sive advances in flower structure from the lower to the higher 

 forms. With this object in view many other details may well 

 be omitted, but some attention should be given also to special 

 modifications of the general plant body. 



(a) Make cross- and longitudinal sections of onion seeds and 

 note the seed coats (integuments) enclosing the rather horny 

 endosperm within which lies the embryo sporophyte. In 

 similar sections of grains of Indian corn the external coat con- 

 sists of the ovary wall grown fast to the integuments; the 

 remainder of the grain consists of endosperm except the elon- 

 gated or shield-shaped "germ," which is the embryo sporo- 

 phyte. 



(6) Sow a niunber of onion seeds and grains of Indian corn 

 and examine one of each every day after germination begins. 

 In the onion note that the plantlet "backs out" of the seed, as 

 it were, the root first appearing, followed by the stem, and last 

 of aU, the single cotyledon. In the corn the cotyledon remains 

 in the grain as a special absorbing organ, so that after the root 



