The following morning the weather was dull and cloudy, and did not look very promising. We determined, however, to visit the Popti La, the pass between Tibet and Nepal, over which all the local traffic passes. Leaving the camp, we entered a small side valley to the South, the path climbing steeply upwards under big rhododendrons (_R. Falconeri_ and _R. Argenteum_) with leaves 18 inches long. Noticing many of their leaves strewn on the path, I inquired the reason for this. Our guide informed us that the carriers fastened these leaves together with thin strips of bamboo and thus provided an excellent waterproof cover for themselves and for their loads. After climbing about a mile, we saw some bamboo huts in the forest and a number of cows were grazing round them. These belonged to some Nepalese herds who come over here in the summer, bringing their cattle to graze. The path now followed the side of a rushing torrent, peaty brown in colour, which came hurrying down under the shade of birch, sycamore, silver firs, juniper and rhododendrons. As we ascended higher, the open spaces became more frequent, though the grass and weeds grew fully 3 feet in height, attesting the constant rainfall of this district. On leaving the path to collect a few seeds from some plants growing a short distance away from it, I found myself in a few moments covered with leeches which apparently thrive here at an altitude of over 12,000 feet; this must be almost a record height for these pests. The path climbed up steeply, the rhododendrons growing gradually smaller in size as we ascended. After going for four hours, we reached the top of the pass--14,000 feet. Here on the top was a stone half hidden in a pile of rocks with a notice, written in Chinese characters, that this was the boundary between Tibet and Nepal. Across the top of the pass was a long wall, mostly overgrown with grass, evidently at one time considered to be some kind of defence. Owing to the clouds being very low, we unfortunately had no view from the top, but just below us, on the Nepalese side, was a fine black lake, about half a mile long, with an island in the centre, which the Nepalese called Dungepokri. On the top were many interesting Alpine flowers, amongst them a charming white potentilla with a red centre; and a large cream-coloured primula, shading into deep orange. We also came across several new varieties of gentians. Here we rested for a couple of hours, hoping that the clouds might lift, but a nasty rain began to fall heavily. While we were waiting several coolies from Nepal passed by: from these we found out that the pass was closed by snow for five months in the year and that the trade market at Sakeding was closed by the end of October. We now turned our footsteps homeward, urged on by cold showers of rain. On the descent we were able to collect a few seeds. Autumn was approaching, though the trees had not yet begun to assume their autumn colours owing to the warm nights.