170 KANSAS ACADEMY OF SCIENCE. 



appear to be over-grown, and the outline of the perfect leaf is frequently plainly 

 discernible before the division is complete. (Figs. 25-29.) It is also interesting to 

 observe that often where a new leaflet has been added, a corresponding notch seems 

 to have been cut from the parent leaf. (Figs. 25 and 28.) Then another leaf is 

 thrown off from the opposite side, taking out a similar notch, thus rendering the 

 terminal leaflet again normal and symmetrical. Lambucus Canadensis, the common 

 Elder, shows remarkable respondence to favorable conditions in the increase of its 

 leafage. The plain pinnate leaves are becoming doubly pinnate, and the minute 

 point at the base of the leaflet sometimes also develops into a considerable leaflet. 

 The leaves of Negundo aceroides, Box Elder, furnish numerous examples of this 

 tendency toward a numerical increase of leaflets. It is not at all unusual to find a 

 graduated series, from one to eleven leaflets. The development of the leaflets of the 

 rose, as stated, proved to l)e an exception to the plan followed by other pinnate 

 leaves, as far as I could find. For a long time search for transition stages was made 

 in vain, when one day while examining the foliage of some tender new shoots, I 

 found the baby leaves in their cradles, as it were. Grant Allen says: "It is the same 

 with plants as with animals; they all pass through a first simple shape, which helps 

 us to picture to ourselves what they once were, so that one of the best ways to dis- 

 cover lost links in the pedigrees of plants, is to watch the development from the 

 seed. The cotyledons, or seed-leaves," he says, " preserve for us still the extremely 

 plain ancestral form, and are the central point from which every variety of foliage 

 -first set out." Young shoots may, perhaps, pass through phases of ancestral forms. 

 Those of the rose certainly seem to indicate that such is the case. When a rose leaf 

 is plucked from the stem two stipules will be noticed at the base of the leaf, and 

 strange to say. these stipules seem to be the little mother-leaves, for the leaflets ap- 

 pear to have originated from them. On young shoots the stipules will often be 

 found to be larger than upon the old wood, and if careful examination is made many 

 may be found having a more or less leaf-like form. The upper jiart of the stipule 

 often assumes the shape and size of the rose leaflet, so that an apparently perfect 

 leaflet is often found still adnate to the stipule; still clinging to it, so to speak, as if 

 loth to be alone in the world. Further development is indicated by the division or 

 separation of the leaflet from the stipule, and as the division continues and new 

 leaflets are thus added, the rachis elongates to make room for the newcomers. (Il- 

 lustrated by figs. 12-20.) Very many specimens were found, illustrating all stages 

 of division from the stipules. Besides this peculiar manner of increasing the number 

 of leaflets, a few specimens were found in which additional leaflets appear to have 

 been quite irregularly added at the base of the leaflets. No transition stages were 

 found in this case — simply the perfect leaves, as seen in the fourth leaf of four- 

 leaved clover. 



Leaves in process of evolution seemed calling for recognition on every side. In 

 the fields and woods, along the road-sides, in the flower-bed and the vegetable gar- 

 den — everywhere interesting specimens were found. The leaves of the cultivated 

 dahlia and those of the potato, tomato and bean all illustrate this tendency. On 

 very many plants where entire leaves ordinarily obtain, notched or obviously-lobed 

 leaves are often found. Examples of such frequently occur on symphor icarpus 

 raeemosi(s (snowberry). Again, on jjlants bearing slightly lobed leaves many are 

 found quite deeply and conspicuously lobed. An interesting example is furnished 

 by the leaves of the wild grape (shown in figs. 30, 38). Cimicifwja racemosa, which 

 has decompound leaves, furnishes a good illustration of both partial and complete 

 division. It is extremely interesting to observe the symmetry which obtains in the 

 various leaf divisions. The mother-leaf, so to speak, usually gives off a new leaf on 

 one side, then appears to liusband her energies until she is able to form a correspond- 



