276 MORPHOLOGY 
tegument belong to the sporophyte, these embryos arise by sporophyte 
budding. A remarkable case is that of an Allinm (onion) with live 
embryos in the sac : one from the fertilized egg, one from a synergid, two 
from the antipodals, and one from the integument. There are thus four 
possible ways by which embryos may appear in an embryo sac: (i) 
from a fertilized egg, (2) by parthenogenesis, (3) by vegetative apogamy, 
and (4) by sporophyte budding. 
CLASSIFICATION OF ANGIOSPERMS 
In so vast a group as angiosperms, it is impossible to present so com- 
plete a classification as was given for the gymnosperms or even for the 
pteridophytes. However, it seems necessary to indicate the larger 
groupings. The scheme presented is known as that of ENGLER, and al- 
though it will doubtless be very much modified, it will serve to introduce 
the great groups. 
MONOCOTYLEDONS 
Among Monocotyledons about 25,000 species are recognized, which 
are distributed among 42 families; and these families are grouped into 
ten great alliances. These alliances may be considered under two cate- 
gories, six of them having spiral flowers (with indefinite numbers), and 
four of them having cyclic flowers (with definite numbers). The spiral 
alliances are regarded as the more primitive, and the cyclic alliances 
represent the more advanced monocotyledons. The six spiral alliances 
are as follows : 
1. Pandanales (3 families, 100 species). The screw pine is the 
representative form, but the cat-tail flag (Typha) is a representative in 
our flora. The group is regarded as low in rank, which means either that 
it is primitive or reduced, because it has naked flowers with indefinite 
numbers, and is wind-pollinated. Another noteworthy feature is that 
the flower cluster is protected by the sheathlike base of the leaf. 
2. Helobiales (7 families, 235 species). This is also an aquatic and 
wind-pollinated group, whose lowest members have naked flowers, as 
the pondweed (Potamogeton), but whose higher members have a calyx 
and corolla, as the water plantain (Alisma). In this group, also, the 
sheathing base of the leaf encloses the young flower cluster. 
3. Glumales (2 families, 7000 species). These are the grasses and 
sedges, which form one of the greatest of angiosperm alliances. While 
there are aquatic members, it is chiefly a terrestrial group, covering the 
