The Cactaceae | Monograph | 1919 -1923 | Landmark Studies

The Cactaceae is a monograph on plants of the cactus family written by the American botanists Nathaniel Lord Britton and Joseph Nelson Rose and published in multiple volumes between 1919 and 1923. It was landmark study that extensively reorganized cactus taxonomy and is still considered a cornerstone of the field. It was illustrated with drawings and color plates principally by the British botanical artist Mary Emily Eaton as well as with black-and-white photographs. Source Wikipedia

Online ( Volumes 1-4) as an independent effort by Mr. Schweich

First page image states main lines of investigation of the study.

I live in the land of saguaro cactus so it was of my special interest to find out a description of the giant of the Sonoran Desert as it appeared in this book more than 100 years ago .

"The flowers of the sahuaro are borne at the crown of the main trunk and the lateral branches, usually appearing in May, while the fruit matures some weeks in advance of the summer rainy season. The small seeds are borne in great profusion, but are eaten by birds and ants so rapidly that the crop is seriously decimated before the requisite conditions for germination occur. The seeds germinate readily at the high temperatures of the summer rainy season, but the growth of the seedlings is extremely slow, so that the end of the second year finds them only one-fourth of an inch in height, and at an age of 8 to 10 years they are still less than 4 inches high. The growth continues to be slow up to a height of 3 feet or more, so that individuals of that size are approximately 30 years of age. After reaching this size the growth rate is rapidly accelerated until it reaches a maximum of about 4 inches per year. The largest individuals are 150 to 200 years of age.

"The sahuaro appears to suffer from very few diseases and natural enemies, the greatest decimation in its numbers being occasioned by mechanical agencies. When struck by lightning or wounded in any other manner during the dry season, it recovers very rapidly by the formation of a heavy callus over the wounded spot. If it is wounded in the rainy season, however, bacterial decay sets in very rapidly and a large plant may be destroyed in less than a week as a result of a small wound. The nests made in them by woodpeckers are always lined by heavy callus and appear to occasion no permanent injury.

"The roots of the sahuaro are shallowly placed and widely extended, often reaching a distance of 50 to 60 feet from the base of the plant. The woody tissue may be compared to a series of bamboo fishing rods arranged parallel to each other in the form of a cylinder. These woody rods increase in thickness with the age of the plant, so that they form a very substantial framework at the base while they taper at the summit to slender elastic rods. The fleshy tissue is found both within and outside the circle of the woody rods and the water content of these two regions appears to be the same. Determinations made near the top of the plant indicate that there is 98 per cent of water on the basis of the net weight. There are great fluctuations in the water content of the tissue from season to season and it has been shown that large quantities of water are taken up during the rainy seasons, particularly in the summer, and that this water is gradually lost during the dry seasons, particularly in May and June. The sahuaro, like many other cacti, is able by reason of its external form to adjust its size to these fluctua- tions in volume.

"This plant is an extremely useful one to the aborigines of its natural range. The heax'y rods are used as construction material in building houses and enclosures, and the fruit and seeds are used for making both food and drink by the Papago and Pima Indians."

Hiking among saguaros - put it on your bucket list :-)