2i6 Referate. 



ein eigenes Gepräge, zwischen den sich scharf befehdenden Richtungen des 

 ,, Galtonismus" und des „Mendehsmus" eine mittlere Linie schaffen zu woUen. 

 Wie weit der Verf. damit den Weg der zukünftigen Entwicklung richtig vor- 

 ausgefühlt hat, bleibt abzuwarten. — Äußerlich ist zu betonen, daß Lecks 

 Buch jedem Gebildeten ohne weiteres verständlich ist, wenn es gleich auch dem 

 Fachmann ein schätzbares Hilfsmittel für Vorlesung. Kursus und Nachschlagen 

 bietet. P o 1 1 - Berlin. 



Leavitt, R. G. A vegetative mutant, and the principle of homceosis in plants. 



Bot. Gaz. 47. 1909. pp. 30 — 68. 



The writer discusses at considerable length vegetable phenomena that 

 are thought to be of the same type that Bateson has described so tho- 

 roughly in animals and to which he gave the name homceosis. Briefly, it 

 may be said that the term is applicable to those cases in which characters 

 originating in one part of an organism are translocated to other parts. 

 The author was first led to this explanation by finding that the same 

 complicated process of abscission that must have originated at the base 

 of the petiole in Aesculus hippocastaiium L. and other plants where the process 

 is essential to the plants economy, also occurs in the petiolules, although 

 such leaflet abjection is there apparently useless. 



Later, his attention was attracted by changes that have occurred in 

 the Boston fern. Several new sports from this wellknown species appeared 

 in the greenhouses of F. R. Pierson & Co., Tarry town- on-Hudson, N. Y., 

 U. S. A. The changes which took place all may be classed as imitative or 

 homoeotic phenomena. The pinnae have divided again and the pinnules 

 in every way represent the original pinnae even to disarticulation by the 

 development of an absciss-layer. In certain cases the progression has 

 continued one step further and even the pinnules have divided. 



Facts such as these are believed to establish the important truth "that 

 a character perfected in the course of evolution under one relation in the 

 plant body may make its appearance suddenly under another relation and 

 in a region of the body to which it is not native." 



The varied data that the author has compiled to support this thesis 

 are divided into ten categories, although several of these are merely partial 

 phases, or explanatory of the others. 



1. Acropetal translocations. Cases where foliage details (toothing, 

 hairing, etc.) have appeared on the floral leaves. 



2. Basipetal translocations. These are the opposite of the above. 

 The change is among the floral parts, or from the floral parts to the 

 involucre or even to the fohage. 



3. Lateral translocations. These are illustrated by both regular 

 and irregular peloria. 



4. Partial invasion of migrating characters. These cases 

 may be illustrated by carpels that approach a petiolate condition. 



5. Migrating characters that transgress the boundaries 

 of homology. This division includes changes where the fundaments of 

 ovules develop into shoots, pistils, stamens, foUage, etc. 



6. Partial imitations of non-homologous organs. 



7. Homoeotic changes that pass from one to the other of 

 the alternating generations. A sporophytic form may be imposed 

 upon a gametophytic cell basis, or vice versa. An example of the first 



