212 A TEXT-BOOK OF BOTANY 



able to endure the cold of winter (Figs. 30 and 31). As 

 there is no regular period for the fall of leaves, as in the 

 deciduous trees, the trees are always clothed with them, 

 and hence are called evergreens. A notable exception to 

 the evergreen habit of conifers is that of the common larch 

 or tamarack, which sheds its leaves every season. 



The great body of the plant is highly organized for work, 

 with its roots, stem, and leaves, and an elaborate vascular 

 system connecting them all. The wood of the conifers is 

 peculiar in its very regular grain, splitting easily; and its 

 generally "soft" character is quite distinct from the so- 

 called "hard woods." Throughout the body there are 

 also numerous resin-ducts, whose contents give a peculiar 

 aroma to the wood. 



123. Strobili. The cones borne by the conifers are 

 well known, and suggest at once the strobili of certain 

 Pteridophytes. There are two kinds of strobili, however, 

 one being the conspicuous seed-bearing cones of common 

 observation, the other much smaller and much less per- 

 sistent cones (Fig. 202). In Selaginella ( 118), it will be 

 remembered, there are two kinds of sporangia in a single 

 strobilus; but in conifers these two kinds of sporangia are 

 in separate strobili or cones. In describing the two cones 

 the pine may be used as an illustration. 



The small cone (Fig. 202, d, and Fig. 203, A) is made 

 up of sporophylls that look like small scales; and on the 

 lower surface of each scale there are two sporangia (Fig. 

 203, B and C), each sporangium containing very numerous 

 small spores (microspores). All of these structures received 

 names long before their relations to the lower plants were 

 known; but as these names are well known it is convenient 

 to use them. The small spores were called pollen grains or 

 simply pollen; the sporangia containing them were called 

 pollen sacs ; and the sporophyll bearing the sporangia was 

 called a stamen. The strobilus or cone, therefore, is a 



