[ch. 11, p. 227 of pdf]
"In so-called 'occult' literature you have probably met with the expression 'Kundalini,' 'the fire of Kundalini,' or the 'serpent of Kundalini.' This expression is often used to designate some kind of strange force which is present in man and which can be awakened. But none of the known theories gives the right explanation of the force of Kundalini.
"Sometimes it is connected with sex, with sex energy, that is, with the idea of the possibility of using sex energy for other purposes. This latter is entirely wrong because Kundalini can be in anything. And above all, Kundalini is not anything desirable or useful for man's development. It is very curious how these occultists have got hold of the word from somewhere but have completely altered its meaning and from a very dangerous and terrible thing have made something to be hoped for and to be awaited as some blessing.
"In reality Kundalini is the power of imagination, the power of fantasy, which takes the place of a real function. When a man dreams instead of acting, when his dreams take the place of reality, when a man imagines himself to be an eagle, a lion, or a magician, it is the force of Kundalini acting in him. Kundalini can act in all centers and with its help all the centers can be satisfied with the imaginary instead of the real. A sheep which considers itself a lion or a magician lives under the power of Kundalini.
"Kundalini is a force put into men in order to keep them in their present state.  If men could really see their true position and could understand all the horror of it, they would be unable to remain where they are even for one second. They would begin to seek a way out and they would quickly find it, because there is a way out; but men fail to see it simply because they are hypnotized. Kundalini is the force that keeps them in a hypnotic state. 'To awaken' for man means to be 'dehypnotized.' In this lies the chief difficulty and in this also lies the guarantee of its possibility, for there is no organic reason for sleep and man can awaken.
[1. Gurdjieff talks about this "kundabuffer" in All and Everything, Beelzebub's Tales to His Grandson.]
[ch. 12, p. 262 of pdf]
" 'New birth,' of which we have spoken before, depends as much upon sex energy as do physical birth and the propagation of species.
" 'Hydrogen' si 12 is the 'hydrogen' which represents the final product of the transformation of food in the human organism. This is the matter with which sex works and which sex manufactures. It is 'seed' or 'fruit.'
[2. See images below. ]
" 'Hydrogen' si 12 can pass into do of the next octave with the help of an 'additional shock.' But this 'shock' can be of a dual nature and different octaves can begin, one outside the organism which has produced si, and the other in the organism itself. The union of male and female si 12 and all that accompanies it constitutes the 'shock' of the first kind and the new octave begun with its help develops independently as a new organism or a new life.
"This is the normal and natural way to use the energy of si 12. But in the same organism there is a further possibility. And this is the possibility of creating a new life within the actual organism, in which the si 12 has been manufactured, without the union of the two principles, the male and the female. A new octave then develops within the organism, not outside it. This is the birth of the 'astral body.'
"You must understand that the 'astral body' is born of the same material, of the same matter, as the physical body, only the process is different. The whole of the physical body, all its cells, are, so to speak, permeated by emanations of the matter si 12. And when they have become sufficiently saturated, the matter si 12 begins to crystallize. The crystallization of this matter constitutes the formation of the 'astral body.'
"The transition of matter si 12 into emanations and the gradual saturation of the whole organism by it is what alchemy calls 'transmutation' or transformation. It is first this transformation of the physical body into the astral that alchemy called the transformation of the 'coarse' into the 'fine' or the transformation of base metals into gold.
"Completed transmutation, that is to say, the formation of the 'astral body,' is possible only in a healthy, normally functioning organism. In a sick, or a perverted, or a crippled organism, no transmutation is possible."
Also see: Gurdjieff on the Abuse and Use of Sex: gurdjieff-on-the-abuse-and-use-of-sex.htm
Diagrams are from In Search of the Miraculous, chapter 9
Hydrogens - human scale - transmutation of energy in the body, illustrated as a "three story factory". Range is 768 to 6.
Hydrogens - cosmic scale. Range for plants begins at 768.