214 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
ON SELF-STERILITY. 
By Professor Dr. F. Lupwie, the University of Greiz, Germany. 
For years I have devoted particular attention to those plants which 
are sterile when pollinated with their own pollen, and have discovered 
that self-sterility is far more prevalent in the plant kingdom than has 
hitherto been imagined; that this, and not an entire loss of sexuality, 
is the cause that many species of plants in extensive districts or on an 
entire continent never, or scarcely ever, form seed; and, finally, that 
within the same species self-sterile individuals may be found in one 
place and self-fertile ones in another. Some of my observations and 
experiences are as follows. 
Self-sterility I have found to occur with special regularity in the case 
of such plants as propagate themselves vigorously by means of rhizomes, 
offsets, or bulbils. The numerous plants which, in the course of years, I 
have raised from one individual—in the case of Symphytum bulbosum, 
Dentaria bulbifera, Apocynum hypericifolium, A. androsemifolium, 
Cypripedium Calceolus, &e.—never set seed in my garden, despite the 
presence of their proper pollen-carrying insects, and despite artificial 
transference of the pollen from bloom to bloom. When, however, in the 
case of Apocynum hypericifolium and A. androsenufoliwm, 1 brought 
plants into the garden from another source, the seed ripened. Jt is 
known also that Dielytra spectabilis, Lysimachia numnvularis, and other 
plants are mostly propagated asexually, and then remain infertile. With 
Ficaria verna, which Schulz found to be gynomonecious, and Delpino 
gynodicecious with smaller female flowers (gynodimorphic),* and espe- 
cially from the results obtained by Herm. Miller, who raised normal seed 
capable of germination from a bulbil-bearing plant, there can scarcely 
remain a doubt that the infertility springs from self-sterility, and that 
this can be removed if pollen from a foreign, that is, a physiologically 
independent, individual be applied. The individuals which are found to 
occupy one habitat probably spring, as a rule, from one and the same 
physiological individual being propagated through the free multiplication 
of the plant by epigceous and hypogeous bulbils. Delpino counted on 
one plant fifty-four hypogcous and twelve epigceous, and on another of 
the female form 124 hypogeous and seven epigceeus bulbils. The same 
may be said of our European Acorus Calamus, the examples of which, 
throughout extensive districts, only represent one and the same physio- 
logical individual, owing to their exclusive propagation by the rhizome. 
Seeds have not been observed in Europe so far, as the plant is self- 
sterile; in America, however, the seed ripens not infrequently, and I am 
firmly convinced that by planting American plants in our waters the 
European Calamus would have its fertility restored. Some five years 
ago I planted the American Calamus in a pond near Greiz: it has spread 
* « Dimorfismo del Ranunculus Ficaria. Memoria letta alla R. Accademia delle 
Scienze dell’ Istituto di Bologna nella Sessione dell’ 11 Aprile 1897.” 
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