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College of Forestry 
1. As To the Content of the Plant Kingdom and the 
Relation of Groups to Each Other. 
As you know, the plant kingdom comprises a series of 
great groups of plants as follows: Thallophytes *; plants of 
very simple or relatively simple organization, the so-called 
lower or primitive forms of plant life embracing in general 
aloae and fungi. bryophytes, comprising liverworts and 
mosses. In this group the plant body is constructed on a 
more complex plan (is more highly differentiated) yet not 
possessing the characters which distinguish the higher 
groups. Pteridophytes, true ferns, horsetails, club mosses, 
te.; plants constructed on the plan of seed plan so far as 
regards the possession of a differenti: 
leaf and vascular tissue, and possibility of develope oreat 
bodies (of tree size and longevity in some cases and 
quite generally in the early geological history of the 
group) —but not seed producing plants. | Spermato- 
phytes or seed plants, differing esspecially from pteridc- 
phytes in that they do bear the structure called a seed. 
This group comprises the gymnosperms, a vast assem- 
blage of forms reaching far back in geological history 
but whose modern forms comprise especially coniferous 
plants such as pines, firs, spruces, etc., and angiosperms, 
which as botanists say is the most recent and highly differ- 
entiated group of the plant kingdom and the one which dom- 
inates in the earth’s vegetation at the present time. 
Now one can scarcely define these groups without employ- 
ing terms which seem to imply, first that each group has had 
a history of development — a racial history in fact — and 
second, that the development of each group is somehow linked 
up with the development of the other groups. The inference 
is that the plant kingdom as a whole tells a story of develop- 
ment from simple and ancient forms to modern and complex 
forms. We ascribe to Darwin, as you recall, the expression 
1 This rather “old fashioned’ method of sub-dividing the plant 
kingdom is retained here chiefly to avoid the use of a more complex 
and bewildering terminology. 
