The 丛林草种子 are a type of 种子 that can be planted in 泥块s to grow Jungle Grass, potentially creating an artificial 丛林 or 地下丛林 (depending on depth) if enough Jungle grass and plants are created. Jungle Grass Seeds can be found by cutting down plants growing on Jungle grass in Jungles using any tool or weapon.
Jungle Grass Seeds can drop from destroying any plant growing on 丛林草. Unfortunately, they have a very low drop rate. Charging through the entire surface jungle cutting down every single plant may only yield a few seeds. It is worth remembering though that Jungle Grass will spread to adjacent open 泥块s just as with any other 草, if slowly. A single planted Jungle Grass Seed can eventually spread through an area of Mud of any size.
It is possible to find the rare items such as 大自然的恩赐s in a player-made Underground Jungle.
The most efficient setup for creating an Underground Jungle "farm" for harvesting 丛林孢子, Jungle Seeds, and Nature's Gifts, is to place a floor of jungle grass, and a ceiling 3 blocks in height. On the next layer up, do the same, but this time also add a middle layer so you have 3 lines with 1 space between each, and repeat. You can then harvest it easily by using a 村正大刀, 草剑, 锤 or similar long reaching weapon or tool to harvest all 3 layers (the one you stand on and the two above it). Note that some items will get stuck above, but will be collected as you rise up the farm layers.
This method is sometimes questioned due to the vines that can hang down and prevent some items spawning. However, in Underground Jungle biomes, grass and roses seem to grow faster than vines, so this should result in better yields in a smaller space than a simple 3 block high tunnel farm. An additional row of 木平台s right under the ceiling will prevent vines from growing altogether, while also letting the players enter without increasing the height of the farm.