254 BOTANY. 
herbaceous annuals to large woody perennials. It is a most 
difficult matter to arrange so great a number of species 
satisfactorily, so as to show their mutual relationship. 
They have been grouped into about one hundred and sixty 
orders. The orders, again, have been grouped as far as 
possible in such a way as to bring together those which 
bear the closest resemblance to one another. The disposi- 
tion of these groups is as yet partly artificial, in many 
cases resulting in the separation of orders which are evi- 
dently related. 
534. The following synopsis will show the latest arrange- 
ment, as generally adopted in‘ this country. For conven- 
ience three artificial groups are made, viz., Apetale, Gamo- 
petale, and Choripetale. 
I. ApeTaALa, APpETALOUS DicoTYLEDONs. 
Plants whose flowers generally have but a single floral envelope 
(calyx) this even, in some cases, wanting. 
Many of the orders here brought together are related to those to be 
noticed further on. Their flowers are in many cases to be regarded 
as simplified Choripetale, or less commonly Gamopetale. The 
grouping given below is almost entirely artificial. 
Series I. . —Flowers mostly unisexual. Perianth none or 
small. A group of anomalous orders of doubtful relationship. 
Order 1. The Hornworts (Ceratophyllacez) are a few small aquatics, 
widely distributed. The seeds contain a well-developed embryo and 
no endosperm. 
Order 2. The Crowberries (Empetracese),—These are four small 
Heath-like shrubs producing berry-like fruits whose seeds contain a 
small embryo in copious albumen. 
Order 3 (Lacistemaces), shrubby plants (16 species) of tropical 
America, producing dry fruits whose seeds contain a copious endo. 
sperm. 
Order 4, The Willows (Salicaces) are trees and shrubs common in 
the Northern Hemisphere. They include also the Poplars, there being 
150 or more species of true willows and 18 poplars now known. 
The flowers are unisexual, and the staminate and pistillate forms 
always occur on different planis (i.e., they are dicecious); they are 
