ANALYTICAL KEYS 



The shrubs described in the text belong, without exception, to 

 the division of plants known as Spermatophyta. They bear true 

 flowers which contain either pistils or stamens, or both, and produce 

 seeds which contain embryos. By two genera, they represent the 

 Gymnospermae ; by one genus, they represent the Monocotyledones ; 

 and, by all other genera, the Dicotyledones of the Angiospermae. 



Although they can be identified most easily by means of the arti- 

 ficial characters used in the genus key beginning on page 17, their 

 botanical relationships are more accurately expressed by the natural 

 key below, which leads to their families. The shorter keys given, 

 where necessary, under the individual families, lead to genera; and, 

 under genera, keys lead to the species. 



« 



Natural Key to the Shrub Families 



I. Gymnospermae 



Ovules and seeds borne in an open bract; stigma 



wanting. 



A. Pistillate flowers borne singly or in pairs, each developing 



into a berry-like fruit Taxaceae, p. 25 



A. Pistillate flowers in small, few-bracted catkins, each catkin 



maturing as a berry-like fruit. Juniperus, in the Pinaceae, p. 26 



II. Angiospermae 



Ovules and seeds borne in closed ovaries ; one or more 



stigmas present. 



A. Monocotyledones: Flowers with 3 petals and 3 sepals, 

 dioecious; staminate flowers with 6 stamens; pistillate 



flowers with 3 united carpels and 3 sessile stigmas 



Smilax, in the Liliaceae, p. 28 



A. Dicotyledones: Flower parts commonly in 4's or 5's, at least 

 not in regular whorls of 3. 

 B. Corolla wanting; calyx present or absent. 



C. Calyx wanting; both staminate and pistillate flowers in 

 catkins. 

 D. Fruit a 1-celled, many-seeded pod ; seeds hairy 



tufted Salicaceae, p. 34 



D. Fruit nutlike, 1-seeded ; seed not hairy 



tufted Myricaceae, p. 59 



C. Calyx present at least in either staminate or pistillate 

 flowers. 



E. At least the staminate flowers in catkins; fruit a nut 



or achene Betulaceae, p. 61 



E. None of the flowers in catkins. 



F. Carpels 2, united ; stigmas 2 ; ovary 1-celled and 



1-ovuled Ulmaceae, p. 69 



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