We are discussing the substitutes to show indirectly what was believed to have been the active principle in the original plant itself. Sat. Brahmana (p.354) implicitly admits it to be growth-soul, for Growth=Life, whence the life-essence can best he designated, growth-soul. Accordingly we read that the worshipper of Soma "strikes sand by two verses containing the verb to grow, whence the seed grows for Soma is breath and puts breath into the seed." Strange enough Eggeling did not realize that Breaths Life-essence and what Soma actually did was to put "life into the seed", rather than breath. It is the life in the seed that expresses itself as growth. Having been positively informed that Soma is rich in growth-soul this would qualify the plant as perennial, to harbour soul maintaining eternal growth. This would easily lead us to plants which are exceptionally tough and can persist where others are delicate and would easily succumb. Satapata Brahmana (Eggeling, 1886, pt II, p.421) gives five substitutes of Soma, one after another. Of them only 'the last two can be definitely identified. What comes as the fourth in order is, Dub, Cynodon dactylon, and as fifth, Kusha, Desmostachya bipinnate. Dymock (1893; Vol.3, p.577) writes that, Dub being a hardy grass it is "always bearing", "Rigveda, X. 134 alludes to its far-spreading habit In Atharvaveda the grass is prayed to for prolonging existence on earth to hundred years" p.577. Kusha and Darbba as Dynock informs us, each has become "a holy grass." He quotes from Atharvaveda: "Thee 0 Darbha the learned proclaim a divinity (mainly because) not subject to death." "At the child's haircutting ceremony, a Brahmin takes three blades of the grass and thrusts them, points foremost, saying 0 herb protect him." Here again is a drug of longevity.
Now one role essentially allied to consecration is that of purification. And the purifying agency is the vivifying agency for what ejects mortality easily ejects impurity. Hence we read in SAT. Br. (Eggeling 1886;SEB, 26,p.31) that where husband and wife have jointly to perform a sacrifice, the woman is dressed in Kusha grass, the reason being "impure is that part of the women which is below the navel and pure are plants of Kusha grass. Thus having by means of Kusha grass made pure whatever part of her is impure, the priest causes her to propitate the sacrifice" - p.31. Now Sat. Brahmana (11.421) specifies Kusha grass as "any kind of yellow Kusha grass." This is reminiscent of the first ephedra plant used by the Aryans being yellow stalked, the Chinese species. Atharvaveda, 20.142.4 also states that "Yellow stalks give forth the juice as cows from udders pour their milk." And there are many such references for yellow stalk in Rigveda already cited.
The active principle of Kusha grass then, is characterized by its toughness. Its roots go even up to five feet deep, most difficult to eradicate, thus indicating its power to endure life. Dymock (1893;575) writes that "it was a holy grass for the purification of the sacred beverage, Soma, and like the Verwain, amongst the Romans, In the Vedas, it is often invoked as a god: Thee 0 Darbha (Kusha) the learned proclaim as a divinity not subject to age or death" - Quoted by Dymock from Atharvaveda. The explanation of Kusha being a substitute of epliedra is that both are perennianal plants and both exceptionally hardy. Such a substitute then makes both emblematical of longevity. This further becomes clear when Frazer (1944; 47) tells us that the "roots of cat-gut are so tough as to stop plough share in the furrow. The Cerokee women (among Red Indians) wash their heads with the decoction of the roots to make the hair strong and ball-players wash themselves with it to strengthen their muscles." Here the Doctrine of Signatures seems to have been applied, maintaining that the plant easily speaks what it is good for. Hardiness would lead to longevity and Soma as a perennial plant has been thus characterized. R.V. 10.94.10 says "strong is your stalks (of Soma) 0 press stones," while 10.175.3 pictures the strength of the plant as being "bull-like". We can then equate Toughness=Longevity which forms the basis for substituting Soma by Kusha. Ephedra would thrive, on dry and rocky soils in contrast to those seeking well-watered plains. Due to its hardiness Soma would be the very opposite of a mushroom, soft and spongy, the easiest to be crushed as discussed before. The Indian substitutes of Soma have been perennial and hardy plants, and not soft or spongy by any means.