ORCHIDS 299 



is said to be ''inferior.'' The nearl}' 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 AmaryUis, but the 

 perianth is made up of unequal 

 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 ^'^- ■^^fu^^nd or ^[pfP"^^ 

 species. 



546. In all the foregoing Monocotyledons the embryos 

 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 witliin which lies tlie embrj'o sporoi)hyte. 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 number 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 tlie seed, as 

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

 of all, tlie single cotyledon. In the corn tlie cotyledon remains 

 in the grain as a si)ecial absorbing organ, so that after the root 



