THE EMBRYO OF THE ANGIOSPERMS. 
& HAROLD L. LYON. 
THE angiosperms are the dominant plants of present floras, 
and were the first to be thoroughly studied by botanists. The 
seed habit, providing a definite period for embryonic develop- 
ment, and the large embryos, often obtaining as a result, made 
the embryology of the angiosperms especially easy and attrac- 
tive. Simple lenses and primitive technique served for the 
study of these embryos, and a knowledge of them was well 
advanced before better instruments and better methods were 
employed to elucidate the embryogeny of lower forms. 
The angiospermous embryo was early hit upon as furnishing 
fundamental data for systematic classification. This quickly 
brought such embryos into prominence in botanical literature, 
and controversies immediately arose as to the morphological 
values and homologies of the embryonic members. While a 
creed, serviceable and satisfactory to the systematists, was soon 
evolved, the chief questions in morphology have continued to 
the present day quite unanswered. The aspect of the problem 
has changed from time to time with increasing. knowledge and 
if we would now attempt a solution we must strive to answer 
the three following questions. 
Are the angiosperms monophyletic ? 
Are cotyledons true leaves ? 
To what structure, if any, in the monocotylous embryo are 
the cotyledons of a dicotylous embryo equivalent ? 
An answer to the last question is, of course, the one most 
generally desired ; but to discuss this question one must take 
some position as to the phylogeny of the classes of angiosperms 
and to the morphological value of cotyledons. 
ARE THE ANGIOSPERMS MONOPHYLETIC ? 
It had been so generally conceded that the angiosperms have 
a common ancestry that in a former paper the writer (: 02) dis- 
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