174 PROCEEDINGS OF THE ACADEMY OF [1897. 



passing notice. That they are not oftener the parents of a line of 

 new species is probably owing to the fact that of the millions of 

 seeds produced by a single plant, an extremely small percentage 

 ever get the opportunity to grow and again develop to a seed-bear- 

 ing condition. There would be little chance among so many for 

 these exceptional flowers of Pentstemon to perpetuate themselves. 



Though it would seem that in this case environment, as it is gener- 

 ally understood, could have had little to do in developing an irregu- 

 lar to a regular flower, one may plead for life-energy as the chief 

 factor in the production of form, and still leave considerable for en- 

 vironment to do. One cannot well retain as erect a position when 

 holding an umbrella against a driving storm, as if he were simply 

 shading himself on a calm summer day ; and there must be some 

 opposing elements or adverse circumstances capable of depressing 

 life-energy as a mechanical force, and with this variation in degree, 

 we may reasonably look for a change in form. But granting all 

 this it must be evident that life-energy, dependent on varying phases 

 of nutrition, is the main power in deciding form. 



SPINES IN THE CITRUS FAMILY. 



The spines which often occur in members of the Aurantiacese or 

 Citrus family are said to be axillary. We are to understand by 

 this that they are situated between the base of the leaf and the axis 

 or stem ; but they are rather lateral than axillary. Lateral spines 

 are to be considered as of stipular origin, but stipular spines are 

 usually in regular pairs, one on either side of the petiole. A single 

 lateral spine could scarcely be stipular. Pondering over these 

 anomalies with an orange tree before me, it was noted that the 

 spines varied much in size and strength. In many cases there were 

 no attempts to form spines at the nodes. In a few instances where 

 spines were wanting, the axillary buds were pushing into growth, 

 where a small point with an articulation might be noted on the bud 

 scale. In some cases there would be points on two separate bud 

 scales. With this suggestion a careful examination of the spines 

 showed clearly that they were but strongly developed bud scales, .or 

 portions of the calycine system. I could trace no articulation as in 

 the young state above noted, though the upper portion soon loses its 

 vitality, while the major part of the spine remains green and active 

 for a long time. 



