552 Atmospheric Moisture of Hot-houses, 



them by their flowers only increases the difficulty of arranging 

 them on a satisfactory basis. 



In consequence of this false standard, we have grouped to- 

 gether the most anomalous forms ; and this entirely destroys 

 the associations rising in the mind in reference to the meaning of 

 the typical names of the groups, which in itself is a great 

 hindrance to the memory ; thus, Echinocactus is associated in 

 the mind with a hedgehog and a prickly plant ; that is, a round 

 prickly plant. Instead of adhering to the unity of the expres- 

 sion, by having all the plants in the section representing the 

 meaning of Echinocactus, we have plants included in the sec- 

 tion from 1 ft. to 20 ft. long. This, of course, does away with 

 the idea of a round prickly plant like a hedgehog. The names 

 Melo- and Echino-cactus literally convey the very same meaning ; 

 that is, round or oval prickly plants. Their application is so 

 far unfortunate ; yet, if the Echinocactus-flowering cereuses were 

 kept apart from them, little confusion would arise by the adop- 

 tion of the two names. 



Through the difficulty of reconciling a group of true Echino- 

 cacti with the false character laid down for that section, 

 Professor Zuccarini lately established another genus, called 

 Echinopsis, to include all the tube-flowered Echinocacti. The 

 meaning of this new typical name, when applied in contra- 

 distinction to that of Echinocactus, is little short of absolute 

 nonsense ; yet it is admitted by Link and Otto in their new 

 work on Cacti, reviewed in your last Number, p. 522. More 

 difficulties may be expected as new species are introduced. 

 The true and natural way of dealing with this section, as well 

 as with the other sections of Cacti, is, to fix on their outward 

 forms for sectional characteristics, as Dr. Lindley justly remarks 

 in the Botanical Register for last May, tab. 24. Their flowers 

 might then very naturally divide them into subsections. 



One might easily show how to arrange these subsections ; 

 but, very likely, most of your readers think they have enough 

 of prickly plants for the present. I have in practice met with 

 the difficulties which gave rise to these observations, and can 

 assure the reader no personalities are meant. 



Kingsbury Gardens, Sept. 7. 1839. 



Art. VII. On the atmospheric Moisture of Hot-houses ; on the Ma- 

 nagement of Orchidaceous Plants ; and on gathering and packing 

 Qrchidece for long Voyages. By D. Beaton. 



In reference to Mr. Wailes's letter (p. 506.), I wish he had 

 fixed on some one else, who may have more time on his hands 

 to do justice to his proposition of horticultural meteorology. I 



