Mr. Douglas in great abundance in North America, from 

 Lake Winipeg to the Western Ocean, between 38° and 49"^ 

 of northern latitude. It has now ahnost become naturaHsed 

 in the Garden of the Horticultural Society, where our 

 drawing was made. If sown at different seasons, it will 

 continue to flower during the whole year, excepting the 

 severest months of winter. 



r 



The genus Collomia, like several other genera of Po- 

 lemoniaceae, is remarkable for a mucous matter in which 

 the seeds are enveloped : if the seeds are thrown into 

 water, this mucus instantly dilates and forms around them 

 like a cloud, and in a short time acquires a volume 

 greater than that of the seed itself. Upon examining the 

 cause of this singular phenomenon, it will be found to depend^ 

 upon the presence of an infinite multitude of ej^ceedingii/ delicate 

 and minute spiral vessels, lying coiled up, spire within spire, on 

 tlie outside of the testa ; when dry, these vessels are confined 

 upon the surface of the seed by its mucus, without being 

 able to manifest themselves ; but the instant water is ap- 

 plied, the mucus dissolves, and ceases to counteract the 

 elasticity of the spiral vessels, which then dart forward at 

 right angles with the testa, each carrying with it a sheath 

 of mucus, in which it for a long time remains enveloped, as 

 if in a membranous case. This observation is particularly 

 interesting, inasmuch as spiral vessels are, we believe, 

 now for the first time seen upon the external surface of 

 a vegetable organ ; they have been hitherto supposed to 

 exist solely within the substance of plants, accompanying 

 either the medullary sheath, or the veins which diverge 

 from it, — with one or two exceptions, of which the seed of 



'f 



Casuarina is one. 



J • \u» 



Note. 



There is another very fine species of this genus in the Gardens, likewise 

 discovered by Mr. Douglas in North-west America, and called by him CoU 

 lomia grandifiora. It differs from the present in its much larger flowers and 

 lucid leaves, and may be specifically characterised thus : — 



C. grandijlora; foliis oblongo-lanceolatis integerrimis lucidis ciliato- 

 glandulosis, caule ramoso pubescente, capitulis hemisphericis pruinosis, 

 corolla ventricosa: limbo erecto. 



K,4 



1 



