228 THE ORCHID REVIEW. [Aucust, 1915. 
reduced to a slender layer separating the nucleus from the cell wall. But 
whether the two conjugating cells are externally similar or widely diverse 
the ultimate result is the same, and the question is what are the events 
which precede and follow the fusion of the nuclei, for the two are only 
phases of the same question. The later phase may be taken first. 
The nucleus of the cell is a very definite organ, and has been 
defined as consisting ofa fine network of fibres and a definite number 
of bodies called chromosomes, supposed to be the bearers of hereditary 
qualities. The gametes are only specialised sexual cells, and_ their 
nuclei are only differentiated from the vegetative nucleus by their condition 
and behaviour. Their union originates a new vegetative nucleus, which, 
after an indefinite number of divisions by vegetative bipartition, again 
produces sexual nuclei, and thus the changes are rung from generation 
to generation. 
The fusion of two nuclei in the sexual act is followed by a period of 
quiescence, during which a new cell-wall is formed round the combined 
protoplasmic mass, and the fibres of the united nuclei go through a 
complicated process of development, by which they are completely 
incorporated together before starting on their new cycle of vegetative “ 
activity. This is the act which, after a longer or shorter period of 
quiescence, originates the new generation. One cannot watch the phases 
of the process, but the details have been gathered from the observations of 
numerous independent experimenters in this difficult field, many of which 
have tended to confirm or amplify the records of previous observers. If one 
could place the cells and their nuclei in a sort of observatory hive, and 
watch their workings in the field of a powerful microscope, one might 
describe how it all takes place. As it is, inferences must be made from 
observed facts, which are rapidly accumulating. 
The broad results are open for everyone to read, and nothing is more 
familiar than the way the members of the vegetable kingdom develop 
from the seeds of a previous generation, and how they produce flowers 
and seed for a future one; or, again, the various ways in which they 
may be propagated asexually by sub-division, as cuttings, buds, grafts, and. 
other methods of horticultural practice. 
We must now return to the earlier but unfamiliar phase of sexual 
reproduction, represented by the reduction division, and this brings us to 
the question of hybridisation and reversion, with which we started out. 
The phenomena of reversion can only be demonstrated where the parents 
possess visibly distinct characters, and nothing is now more familiar 
to hybridists. The cause, however, is still to be largely inferred from the 
effects, hence the wide diversity of opinion that has been expressed upon 
the subject. One thing, however, is clear, and that is that the cause of 
