1914] JEFFREY— SPORE CONDITIONS 329 



of Iris germanica. The species of Iris are usually quite free from 

 any indication of hybrid contamination, with the possible exception 

 of Iris Hookeri, which has not been fully studied. In fig. 12, the 

 pollen is largely abortive and is reduced in amount, as is frequently 

 the case in hybrids of all kinds. 



Fig. 13 shows the pollen conditions in Lilium canadense. The 

 grains are here quite perfect. Similar observations were made 

 on Lilium philadelphicum and the common Easter lily. Fig. 14 

 illustrates the pollen abortion which is the usual condition in our 

 cultivated Narcissus, nearly all of which are known to be of hybrid 

 origin. The shriveled and abortive condition of a large number of 

 the grains is quite evident. Fig. 15 pictures the condition of the 

 pollen in Lachenalia Nelsoni, a plant very frequently grown in 

 greenhouses in winter. This hybrid between two natural South 

 African species of the genus was made by an English clergyman, 

 in window culture, many years ago. Most of our garden tulips 

 show their hybrid origin by large quantities of abortive pollen. 

 A very large number of observations has been made upon mono- 

 cotyledonous cultivated hybrids, with the unvarying result that 

 hybridism was characteristically connected with a considerable 

 amount of pollen degeneracy. On the other hand, monocotyledons 

 grown in the greenhouse under obviously somewhat unnatural 

 conditions, where of pure specific origin, showed, in all cases 

 examined, good pollen. This was the case, for example, in species 

 of Gasteria, Agave, etc. 



We now advantageously turn our attention to the very large 

 natural group of Dicotyledons. Here hybridization both natural 

 and resulting from the intervention of man is extremely common. 

 We may first consider with advantage the Rosaceae, in view of 

 Brainerd's very interesting studies on this family. This investi- 

 gator has shown that a great many natural hybrids of Rosa and 

 Rubus occur in nature. The morphological observations made in 

 this family entirely confirm Braixerd's results, and extend them in 

 an apparently very interesting way, which will be summarized here, 

 a fuller account being reserved for future publication. Not only 

 are certain of the Rosaceae recognizable as hybrids, on account 

 of their transitional external features of organization, Mendelian 



