DISGUISES OF LEAVES, CONCLUDED 107 



determine whether the number of leaves in a cluster 

 is characteristic of each.) Are these five bodies 

 leaves, or branches? If the evidence of mere po- 

 sition is proof, however, they are cladophylla, for 

 they are borne in the axils of scales. Each bundle 

 is enveloped at its base ia a sheath, and this 

 sheath, with its leaves, is sometimes plainly axil- 

 lary ; but the sheath is probably homologous with 

 bud-scales. There are morphological reasons, also, 

 for calling them leaves. The point is, that it is 

 often difficult to interpret a given form correctly 

 by the application of an arbitrary rule. 



117a. Let the pupil examine a growing shoot of pine (in spring), 

 and observe the position of the dry scales, which sometimes fall 

 away and leave only the scar-like evidence of their presence. See 

 Obs. Iviii. (In Fig. 105, the sheath has been worn away by the 

 elements.) Let him notice, if, at the base of the new growth, 

 there are scales from which no leaves arise, as there are leaves 

 in similar positions upon other trees from which no branches arise 

 (42^. For further light upon the subject, he will be interested to ex- 

 amine the fascicled (or clustered) leaves Of the larch or tamarack. 



1176. The pupil will now examine the leaves of spruces and firs. 

 These leaves are placed singly, and it is difficult to make them 

 out to be axillary to scales ; and this may throw some light 

 upon the nature of the leaves of the pine. 



117c. The pines and spruces are commonly known as " ever- 

 greens," because they never lose their foliage. This does not 

 necessarily mean, however, that their leaves never fall. In fact, 

 we know that the leaves do fall, for we remember seeing the 

 ground under old pine trees covered with needles ; and we 

 know, too, that the interior of the top of a pine tree is brown 

 and dull, not lively green, as it would be if the leaves were still 

 intact. We should not expect the leaves to persist inaida the 



