The author enters into a more detailed discussion of the mor phological characteristics of the leading types of Cadenza for the purpose of illustrating the structural modifications of the podetium and its relation to the primary thallus and apothecia. Life-size figures of the types accompany this discussion. Reinke quite frequently speaks of " fertile forms" when only " pycnidia" are present, which shows conclusively that he considers these structures as reproductive organs coequal in importance to the apothecia. The fact that the pycnidia (and spermagonia) may occur on either the primary thallus or the podetium, while the apothecia occur on the podetia (excepting a few Claa'onias which are said to have no podetia or only pseudo-podetia) does not seem to raise any question in the author's mind as to the feasibility of considering the former as true sexual organs. This is only in passing, but it is well to remember that sexual organs are gener ally not so variable in their occurrence and position on the vege tative portion as the pycnidia and spermagonia evidently are.
Without going into further details the following summary may be given of Reinke's reasons for assuming that the podetium is a thallus rather than a reproductive organ.
i. A gonidial layer is present whose special function is that of assimilation. This is, however, not conclusive, since all apothecia with a thalloid exciple contain gonidia (algae), and therefore aid in the process of assimilation.
2. The extreme variability in the size and form of the pode tium indicates that it belongs to the vegetative portion of the plant rather than the reproductive portion. Constancy in size and form
is peculiar to the organs of reproduction.
3. The association of a large primary thallus with a small po detium and, vice versa, a small primary thallus (or none at all) with well developed, much-branched podetia seems to indicate that the podetium is specially adapted to supplant the function of the pri mary thallus.
4. Cladonias with highly developed podetia (C. furcata, C. rangi firina, etc.) are quite generally sterile (devoid of apothecia) and with primary thallus rudimentary or wanting. It would be absurd to consider such plants as reproductive organs since their prime function is vegetative.
Reinke admits that the podetia are phylogenetically derived from apothecia and thus in part agrees with Krabbe. The follow ing are the main reasons for assuming that this is the case : 1. Podetia are developed endogenously from the gonidial zone of the primary thallus, similar to the apothecia.
2. Podetia have a radial structure similar to apothecia and apothecial stalks. This is in sharp contrast to the dorsiventral structure of the primary thallus.
3. The apothecia occur upon the podetia. An apparent ex ception is met with in C. miniata in which the apothecia seem to be sessile upon the upper surface or margin of the primary thallus. In this case the podetium has become much reduced, while the primary thallus has become much enlarged.
The general conclusion at which Reinke arrives is that the po is a true lichen-thallus phylogenetically derived fiviu the apothecium.