274 REPORT OF THE CONFERENCE ON GENETICS. 
with locomotive power in water, and, strange to say, similar in every 
appreciable way to the spermatozoids of the animal kingdom. Normally 
the under side of the scale is bedewed with water, and through this they 
make their way direct to the embryo seeds situated a fraction of an inch 
distant, but, naturally, when the pan is flooded at the right time 
multitudes of these organisms are floated, as it were, broadcast, and thus 
have a chance of reaching and fertilising other embryo seeds at a distance. 
We thus see that although it is practically impossible, owing to their 
minuteness, to transfer the fertilising organisms systematically as we can 
the visible and tangible pollen grains, there is nevertheless a possibility of 
forming combinations on selective lines. Selective cultivation of exotic 
ferns, independently of crossing, has, we think, depended more upon the 
fact that the best varieties are naturally sown from, and hence improved 
ones naturally crop up from time to time, than on any systematic lines 
aiming at definite results, and if we study what may be termed trade 
ferns, such as are raised by the million for the market, we find the 
novelties to occur almost entirely among these. The novelties, on the other 
hand, which appear from time to time among the tenderer and rarer exotics 
are mostly imported “ finds,’’ the histories of which, however, it is usually 
difficult to ascertain. A curious fact in this connection is seen in the 
Nephrolepis tribe, which up to a very few years ago had not sported to 
any great extent, when suddenly new types, crested, congested, and plumose, 
succeeded one another so quickly that now there is a considerable range of 
forms, especially in NV. exaltata. WN. e. Piersonvi and its improved form are 
evidently on the way to rival some of the best of our plumose forms of 
Polystichum angulare provided their cultivators do not confine themselves 
to the easy propagation by stolons of which this species permits. By 
spores alone can any great stride be obtained, and, judging by analogy 
with P. angulare, a single generation might suffice to yield abundance of 
far superior forms on finer and finer lines of subdivision. Curiously 
enough I have fronds of N. exaltata, given me at least ten years ago, in 
which most of the pinne are bipinnate on N. Prersonw lines; but 
unfortunately my advice then given as to sowing was not followed, and 
the plant was lost sight of. In this connection, too, | may mention that 
when Gymnogramma Laucheana grandiceps was introduced some thirty 
years ago, the raiser assured me that a large batch of it, all alike, 
originated from spores sown from a merely dilated pinnule on an other- 
wise normal plant, a point which is worth remembering, though the 
experience of selective raisers of British ferns tends to prove that local 
variations of this kind are rarely accompanied by a reproductive capacity 
on like varietal lines. It must, however, be confessed that we are quite 
in the dark as to the cause of these sports; but, judging by the general 
evidence connected with wild sports, they must arise from subtle local 
cell modifications on normal forms, which find expression probably in 
yarious ways, sometimes by bulbils or offsets, and sometimes through 
spores, or the modified sportive cell may even originate in the prothallus 
either in a fertilising antherozoid or an embryo seed. The theory which 
has been put forward that they are due to crossing will nut hold water, 
at any rate in the majority of cases, since they so often occur in species 
which are quite isolated from others of the same genus, and any cross- 
