ILLUSTRATIONS (30). WILLOWS. 341 



is supposed to be effected by means of moveable ciliated spiral 

 threads and not by pollen tubes.* According to this view, 

 Ferns would be, as Ehrenberg remarks.f products of a micro- 

 scopic fructification taking place on the prothallium, which 

 here serves as a fertilizing receptacle, while throughout the 

 whole course of their often arborescent development they 

 would be flowerless and fruitless plants, having a bud- 

 formation. The spores lying as sori on the under side of the 

 frond are not seeds but flower-buds. 



(29) p. 229" The Liliacea." 



Africa is the principal seat of this form ; there the greatest 

 diversity obtains ; there they form masses and determine the 

 natural character of the region. The New Continent exhibits 

 also, it is true, magnificent AlstromeriaB and species of Pan- 

 cratium, Haemanthus, and Crinum. We have enriched the 

 first of these genera with nine, and the second with three 

 species ; but these American liliaceous plants are more diffused 

 and of less social habits than the European Irideae. 



(30) p. 229" The Willow Form." 



Nearly 150 different species of the main representatives 

 of this form, or rather of the Willow itself, are already 

 known. They cover the northern parts of the earth from 

 the equator to Lapland. Their number and their varie- 

 ties of form increase between the 46th and 70th degrees of 

 latitude, more especially in that part of northern Europe which 

 has been so remarkably indented by the early revolutions of 

 our planet. I am acquainted with ten or twelve species of 

 inter-tropical Willows, and these, like the Willows of the 

 southern hemisphere, are deserving of special attention. As 

 nature appears to delight in all zones in a wondrous multi- 

 plication of certain animal forms, as for instance, Anatidai 

 (Lamellirostres}, and Pigeons ; so likewise are Willows, Pines, 

 and Oaks, widely diffused ; the latter always exhibiting a simi- 

 larity in their fruit, although various differences exist in the form 

 of the leaves. In Willows belonging to the most widely dif- 

 ferent climates the similarity of the foliage, of the ramification, 

 and of the whole physiognomical conformation, is almost greater 



* Count Suminski, Zur Entwickelungs-Gescliichte der Farrnkrautei 

 1848, 8. 1014. 

 f Monatl Berichte der Akad. zu Berlin, Janiur, 1848, S. 20. 



