PART I. 



GROWTH AND WORK OF PLANTS. 



CHAPTER I. 



PARTS OF SEEDS AND HOW SEEDS GERMINATE. 

 THE BEAN. 



1. Seed of the common garden bean. There are many varie- 

 ties of garden beans but the form of the seed is often slightly curved 

 or kidney-shaped as seen in side view. Upon the concave side 

 there are distinct markings. There is a scar (= hilum) about the 

 middle line. This is the point where the seed was attached to 

 the wall of the bean pod as can easily be seen in the case of young 

 beans by opening the pods. On either side of the scar is a minute 

 mark. One of these is slightly larger than the other and often 

 appears when examined under a hand lens to be somewhat heart- 

 shaped. It is continuous with a short elevated line on that end 

 of the bean. This slightly elevated line is the 

 raphe (fig. i). It is formed by the stalk of the 

 ovule (the very young stage of the seed in the pod) 

 .which is attached at the end of the bean and 

 here is bent around and joined to the edge. On 

 the other side of the scar and near it is a minute 

 opening, the micropyle. The root of the embryo 

 lies beyond this just underneath the seed coats. Fig. i. 



Its position is often manifest by a prominent ide as primary root- 



elongated elevation especially when the bean is Em^raphe; c. cha- 

 swollen after soaking in water. 



3. Parts of the bean seed. When beans are soaked for a 

 few hours in water the seed coats take up the water faster than 



