I finish my course of Lowell lectures this week, which have succeeded beyond my most sanguine expectations. I have restricted myself to physiological botany only,--taken up only great leading views,--used very large paintings for illustrations, six to eight feet high, which the great size of the room required, and then have given to sound scientific views a general popular interest. TO JOHN TORREY. CAMBRIDGE, May 24, 1844. I have been using Dr. Wyman’s microscope of late, and it works well. By the way, I have been studying fertilization a little, and have got out pollen-tubes of great length; have followed them down the style, have seen them in the cavity of the ovary, and close to the orifice of the ovule. My first views were in Asarum Canadense and A. arifolium, where I can very well see the pollen-tubes with even my three-line doublet! I have seen them finely in Menyanthes; and in the ovary in Chelidonium! I am lecturing[135] in a popular and general way entirely on physiological botany, and offering no encouragement to any to pursue systematic botany this year. My great point is to make physiological botany appear as it should be,--the principal branch in general education. Next year I hope to take up the other branch. I am using the Lowell illustrations (though too large for my room), and am having no additional ones made for the college. For simple things I depend much upon the blackboard. I have given two lectures on the longevity of trees, and have a third yet to give, or at least half of another.... The plants from the mountains have some done well, others poorly. Buckleyas had a hard time of it. Many are dead; none I think will flower this season, as they only put out from the root. Diphylleia, Saxifraga Careyana, a new one like it, also S. erosa, etc., are now in flower. Astilbe is in bud, also Vaccinium ursinum. One Carex Fraseri flowered. Hamiltonia only starts from the root. * * * * * In 1844, finding he needed more room for his rapidly increasing herbarium, Dr. Gray applied for the use of the Botanic Garden house, which since the death of Dr. Peck had been occupied for a while as a boarding-house, and later by Dr. and Mrs. Walker. He moved into it in September, and there remained until the end of his life. He had a great attachment for the house, as the only one in which he had resided for any length of time; and it saw the gradual growth of his herbarium, needing before many years the addition of a wing to give more room, until, having overrun all possible places for its accommodation, it was removed in 1864 into the fireproof building which now holds it.