SUPPLEMENT 



when it has become closed by the seed coats. The knob at one end 

 of the castor bean is the thickened edge of the micropyle and it 

 becomes an excellent absorbing organ. 



It may seem petty to distinguish between the root and stem in the 

 embryo, but it is well to note from the first that leaves are borne by 

 stems, not by roots, and that roots grow from stems, not stems 

 from roots. The technical terms for seed leaves, stem and 

 root, have been omitted until later on in the chapter in order that the 

 real nature of the parts be not obscured. In fact it is only in deference 

 to custom that they have been introduced at all in such an elementary 

 work. The castor bean seedling early gives off side roots at the end 

 of the stem, usually in four groups, each group from a pair of woody 

 fibres, as can be seen from a cross section of the stem. The fact that 

 the growing cotyledons absorb the food, both for themselves and for 

 the rest of the embryo, seems to me to be clearly illustrated by the 

 natural development of the seedling, but the endosperm may be 

 removed from one of two seedlings of equal size and the result noted ; 

 or thiu experiment may be performed with any of the other seedlings. 

 Obviously some of the stored food is in the form of oil, and unless the 

 teacher takes special care, this fact will be recorded in grease spots 

 on the floor. The oil of the castor bean, like starch that forms the 

 bulk of corn, wheat and many other seeds, is not nitrogenous, but all 

 seeds have also some albuminous or proteid substance. This is neces- 

 sary since the living and growing parts of all plants as well as animals 

 contain much proteid material. The endosperm of the castor bean is, 

 in reality, as well as in appearance, similar to cheese, but it is hardly 

 practicable to test proteid substances in elementary work. Oily seeds 

 do not decay so readily as starchy ones, but they germinate more 

 slowly. Still the castor bean gets well above ground in three or four 

 weeks. Some observing pupil may notice the glands at the base of 

 the castor bean cotyledons. These are very marked in the mature 

 plant and will be referred to later on. 



Pine seeds are introduced mainly because of the attractiveness of 

 both cones and seedlings. Seeds of the Monterey pine (Pinus 

 insignis) can be had at seed stores. They germinate almost as rapidly 

 as the castor bean. Pinons are difficult to grow and require much 

 time. Cone-bearers will be taken up again in Chapters VIII and 

 XIII. They constitute an interesting family and have a marked 

 individuality. John Burroughs brings out this idea charmingly in 

 " A Spray of Pine," in " Signs and Seasons." 



Children may be led to trace the other seeds suggested back to their 

 plant homes and to note their devices for protection and distribution, 



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