| THE GROUPS OF ANGIOSPERMS 351 
ame tribe. Then from the bracts preceding these sexual phyl- 
mes, or from the lowest stamens, the perianth was developed. 
lna few scattered tribes of monocotyledons and dicotyledons 
these lower stages are still to be found, but in others, where 
yelical arrangement and definite numbers prevail, they have 
disappeared. We cannot know whether or not the latter pos- 
sssed spiral arrangement of members originally ; indeed, it is 
tot necessary that this should have been the case, for it is pos- 
‘ble that at the very first formation of series, forms with spiral 
tadalso with cyclical arrangement should have arisen. Thus 
‘ration of number could have appeared early in the one and 
ae in the other. 
| Nageli believed that every tribe has proceeded from early 
pes with spirally arranged floral phyllomes. If this were 
‘ue, then the Orchidacez, for instance, would be the oldest of 
“onocotyledon types, and the Umbellifere and Composite very 
| iid types of dicotyledons, for they would have gone through 
the most modifications. However, in my opinion, there is 
- whhing against the view that cyclical arrangement arose in 
“tain tribes from the very beginning. In the most of these 
and series fixation of number probably appeared very 
ay, and of these many afterward suffered modifications by 
| ‘eduction of particular members or multiplication of others. In 
Gh ‘Series in which wind-pollination prevailed, Pandanales, 
: miflorae, Principes, Fagales, a highly developed corolla, 
+ "8 No Particular value, stood no chance of transmission to 
.* snerations following. Modifications could only take place 
gaa directions, particularly in the reduction of the number 
_ which in certain Glumiflore, Piperacee, Salicacee, 
EP mid Chenopodiacew has reached its ey 
ee may also occur in the form of complex ee : 
et Where the perianth is petaloid and insect-po as 
oe become established, finally zygomorphy follows, ii 
: bail, reduction, which attains considerable ini pore in ome 
tee ‘Oy the Pontederiacee, Leguminose, Philydracee, 
ag Although in the reduction of petaloid and hetero 
