164 COMPENDIUM OF GENERAL BOTANY. 



a manner gimilar to the tricliomes or leaves (pbyllome). An un- 

 warranted procedure is to conclude that the reproductive organs are 

 evolved from the vegetative organs, or. as it is usually expi-essed, 

 "are derived phylogeneticallv." The advocates of the theonj of 

 descent either take its correctness for granted or seek to make it ap- 

 ph'cable to this or that case. We shall refrain from going beyond 

 the conclusions based upon observed facts into the realm of 'phan- 

 tasy and pure speculation. Also the classification of leaves as 

 " leaf-forms " is not acceptable to those who wish to consider, for 

 e.xaniple, the cataphyllary leaves as phylogenetically derived from 

 the foliage-leaves.' A few remarks on the ''transition " of vegeta- 

 tive leaves into reproductive organs shall now be added. 



In the first place it is evident that the stamens and foliage- 

 leaves, morphologically considered, are both leaves, yet the differ- 

 ence between them is very great when we consider each as to its 

 function in the mature state, since such a mode of treatment is 

 •aj>propriate here as well as it was in regard to the internal oi'gans 

 (tissue-systems). It is also clear that we cannot conceive of the ori- 

 gin of a stamen other than that it starts as a small wart-like cellular 

 protuberance on the side of the stem. Finally, it is also cleai- that 

 the young stamen will take such a course in its development as will 

 lead to the formation of a pollen-bearing organ rather than of 

 a foliage-leaf. The morphological conception of an organ is justifi- 

 able, but it must not be valued too highly. 



Between the involucre and stamim'ferous flowers of the Com- 

 2)ositai occur the so-called neutral flowers, which to the observer 

 seem to be formations of a double nature. It is, howevei-, evident 

 that in the development of stamens such intermediate states are 

 not passed through ; these neutral organs can hence not be looked 

 upon as states of transHion. Morphology based upon facts of de- 

 velopment points out the great similarity between stamen and leaf, 

 between most carpels with their ovules and divided or compound 

 leaves; this similarity is further emphasized by the frequent occur- 

 rence of the apparent reversion of the floral leaf to a foliage-leaf. 

 Every observer has no doubt witnessed such phenomena. Bnt to 

 conclude that such changes are evidence of the evolution of repro- 

 ductive organs from purely vegetative leaves is wholly unwarranted ; 

 it has not been proven. 



' Westermaier, Natur und Oflfenbaning, 1893. 



