Digitalis thapsi many characteristics of "D. purpurea" after four to five generations of cultivation, and that the former became indistinguishable from the latter, a report that was considered "probably" trustworthy by Charles Darwin. "D. thapsi" and "D. purpurea" hybrids are generally fertile. "Digitalis thapsi" is widespread in Spain. A biennial evergreen plant, it flowers in late spring. A study of the fruiting activity in "D. thapsi" showed that production, size and number of seeds were interrelated. Analysis has shown that seed weight is not related to the length of the cotyledon, and that the length of the fifth leaf can serve as
Plant physiology plants produce a vast array of chemical compounds with unique properties which they use to cope with their environment. Pigments are used by plants to absorb or detect light, and are extracted by humans for use in dyes. Other plant products may be used for the manufacture of commercially important rubber or biofuel. Perhaps the most celebrated compounds from plants are those with pharmacological activity, such as salicylic acid from which aspirin is made, morphine, and digoxin. Drug companies spend billions of dollars each year researching plant compounds for potential medicinal benefits. Plants require some nutrients, such as carbon and