TERMINOLOGY OF REPRODUCTIVE ORGANS IN PLANTS. 11] 
phraseology has caused so much trouble as this one. It 
has always been acknowledged that plants reproduce 
themselves sexually and asexually. We have just seen 
that the union of the sexual cells results in the formation 
of an embryo. The signification of the process of union 
is one on which there are still many diverse opinions. 
Probably that which accords best with the facts of the 
case 1s, that the ovum and the sperm are imperfect, or 
rather complementary cells, each possessing what the 
other wants, to make it a complete and perfect cell capable 
of forming an embryo, and each therefore incapable of 
becoming such without union with the other. I do not 
propose to enter here into the discussion of the functional 
differences between these cells, or the way in which it has 
come about that the sperm has become so differentiated 
in character from the female cell, loosing very early the 
power of receiving a sexual stimulus from other non- 
sexual cells, and so developing into an embryo, a power 
retained by not a few ova, according to the researches of 
Jaworowski* and others. 
Many plants are, however, able to effectively reproduce 
their kind by giving rise, in a variety of ways, to apparently 
perfect cells, which without union with any other cells are 
able to develope into plants like their parents. Such cells 
almost all botanists have agreed to call “spores,” or 
asexually- formed cells. Vines, however (loc. cit.), as 
already stated, considers that these cells are entirely com- 
parable to the fertilized ova, and therefore describes spores 
as of two kinds, asexual and sexual, describing the product 
of union of an ovum and a sperm as a sexually-formed 
spore. There can be no doubt that an embryo or fertilized 
ovum is physiologically equivalent to a spore, inasmuch as 
both are capable of forming an adult plant; but surely 
* Archives Slaves de Biologie, 1886, 
§ 
