THE ORCHID REVIEW. 271 
also observed that the amount of oxidisable matter present in the atmosphere 
had no relation to the quantity of ammonia present. 
I think it is probable that the relation of ammonia to carbonic acid has 
a considerable influence upon the growth of epiphytal Orchids. This is 
the probable cause that many Orchids—such as Oncidium varicosum on the 
one hand, and Phezlenopsis on the other—cannot be kept in vigour for any 
length of time in this country. 
The analysis of old and new pseudobulbs shows that there is less 
mineral matter in old bulbs when compared with the new. Apparently 
these plants have great difficulty in obtaining the earthy salts, and are, 
therefore, obliged to withdraw from the old bulbs some portion of their 
earthy constituents. We know that allowing the flowers to remain on 
the plants until they have withered is followed by the shrivelling of the 
- pseudobulb and with it the exhaustion of the plant; the better the variety 
the more delicate the constitution of the plant and the greater the 
exhaustion caused by flowering. 
It occurred to me that it would be desirable to find out which, if any, of 
the earthy constituents were removed from the pseudobulb by the flowers. 
For this purpose I sent up to my friend, Prof. Ogston, a large number of 
fresh-cut blooms of the largest and best varieties in my collection of Cattleya 
Mendelii, Mossi, and Lelia purpurata. 
Comparing the analysis of the blooms with the composition of old and 
new pseudobulbs, it is evident that a large amount of the mineral con- 
stituents of the pseudobulb are abstracted by the flower. The question 
cultivators have to consider is, in what manner can these plants recuperate 
by the re-absorption of these mineral constituents into their organisms, for 
it is evident if they are not furnished with a means of obtaining a fresh 
supply they will continually withdraw these substances from their old 
pseudobulbs, with a result—impoverished growth, smaller and smaller in 
size, poorer blooms and ultimate death. 
I therefore thought that it would be well to experiment upon an old and 
starved variety of Cattleya Triana. I fed this plant once a week, during 
the growing season, with two or three ounces of water, which contained 
nitrate of potash, nitrate of ammonia, phosphate of ammonia, and carbonate 
of magnesia, of the strength of half-an-ounce of nitrate of potash and half- 
an-ounce of nitrate of ammonia, with a small quantity of the other salts, 
with the result that the plant made stronger growth, produced a greater 
number of flowers, which were brighter in colour. In 1895 I tried a 
larger number of plants, and I was so satisfied with the result that in 1896 
I added nitrate of potash and nitrate of ammonia each week during the 
summer to the rain water tanks of the Cattleya house. The total quantity 
used during the summer was 1b. of the nitrate of ammonia and 1lb. of 
